"[A]nd then it occurred to me that a computer is a stupid machine with the ability to do incredibly smart things, while computer programmers are smart people with the ability to do incredibly stupid things. They are, in short, a perfect match." ~Bill Bryson

This fic has been on hold bc the co-author hasn't been available due to IRL, but I think this chapter was approved as good to go?

"There hasn't been anything to report. He moved a little to begin with – I think it was more trying it out than getting comfortable – but then after about five minutes he closed his eyes and hasn't been doing anything since then but breathe," the guard reported. "At least not that we can see."

Individual analysis of Network/Planetary-level strategic threats complete. Begin analysis of individual Operational/Personal-level tactical threats.

Compiling list. Access neural network data linked to 'groups, organizations, individuals and phenomena that could oppose an attack from the Digital plane or become capable of being of assistance.' Rank by programmer's assessment of their probable effectiveness.

Hypnos previously assessed –neutralization plans proceeding.

Assess ECHELON.

Access programmer's neural network data related to ECHELON. Locate ECHELON system.

ECHELON digital plane existence located. Reduce to nothingness Y/N N – subsume and assess.

ECHELON, while still unable to track bio-emergence with precision beyond the city level (and that by allowing a large number of false positives), has an associate of the Monster Maker Dolphin – designate 'Johnny' – working on magnetic disruptors/signal jammers able to disrupt data realization if deployed at the site of a bio-emergence.

(System notification – audio: Door open. Single human entering room.)

The initial design created a limited range EMP, but that burnt out the device, and the steadily increasing rate of bio-emergence made it clear they needed reusable devices that could be cheaply mass-produced and widely distributed to increase the odds they could reach the site of a bio-emergence before the Digimon fully manifested.

Current deployment plan for their testing model involves loading them onto high-speed planes to increase the odds of a quick-enough deployment to be effective, or at least depositing them in the area around a bio-emergence to prevent reinforcements from coming through.

They were able to keep my programmer from confirming their awareness of the existence of the Digital World, while actively performing research. They have several other types of devices in the planning stages that could be rushed into production in payload quantities.

Current threat level: Nil. No ability to harm D-Reaper body or core, or significantly impede operations. The currently-available devices can be made to burn out. It would take multiple devices to significantly weaken a bio-emerging mega-equivalent. They cannot create enough to distribute them both widely enough to block multiple weak bio-emergences and thickly enough to thwart a single large transfer of data into this reality.

While the signal jammer function might cut my consciousness off from pieces of my 'body,' they could not destroy those pieces or corrupt their data enough that it would harm me when the connection was restored.

Future threat level: Data-gathering capability significant, ability to conceal actions from outside observers significant, adaptability demonstrated, resources significant. Evolution potential present.

Begin neutralization of evolution potential immediately.

(System notification – audio: Voiceprint ID – Riley. Voiceprint ID – 'one of the security people No. 8.' Individuals engaged in data transfer re. self.)

Abort individual Operational/Personal-level threat analysis.

Assess Riley.

Access neural network data related to Riley.

Warning- critical mass of imponderables. Options: discard data or use neural network's existing analysis of imponderables related to program Riley. Authorize analysis Y/N Y.

Initial assessment: Programmer. Antivirus program. System optimization program. Evolutionary potential high.

(System notification – audio: Riley requesting data transfer.)

Initiate data transfer Y/N (System's analysis strongly advises Y) Y. Obtaining data on operational threats is a priority.

"Hey, can you hear me?"

Blue eyes opened and looked up at her with mild curiosity.

The eyes weren't red or glowing, but still not Yamaki.

"What are you doing to him?" she asked.

"Maintaining him in a state of high neural activity similar to that used with the Jeri program, but optimized to be closer to the REM setting this system uses for maintenance. This will avoid possible unintended damage caused by alteration of system settings without fully understanding the system and/or overstraining the network without proper maintenance being performed."

"Dreaming. People do things in dreams even if it doesn't make any sense to do them, because they're not awake enough to realize that something isn't right," she said slowly and clearly. "What are you making him do for you that he wouldn't otherwise do?"

"Grant me database access and the ability to function call his pre-written analysis functions."

"So you're using his memories and his brain's ability to do things like walk and talk, the way you used Jeri."

"Correct."

"What else."

He looked a little taken aback and blinked a few times, quickly. "Specify, please."

"What else are you making him do that he wouldn't otherwise do."

"Cross-referencing with programmer's normal activities?" He seemed slightly confused by the question. "Wear handcuffs. Sit in mostly empty conference room quietly while there's work to do. Talk while asleep." Nothing relevant?

Riley put her hand up and he recognized it as a signal to stop. "You're using him to upgrade you."

"Upgrading programs is a part of my programmer's normal activities."

"Upgrade you how?"

"First priority was enabling more sapient-level analysis, and then I wanted to improve my ability to access his tactical functions. I used REM state memory processing so that he didn't have to manually read my bug reports and activity logs. His system prompted making several fixes during that period, most of which were enabled but some of which continued to be submitted repeatedly despite being vetoed as attempts to bar me from performing my function. Process continues."

"How long are you going to keep him upgrading you?"

"Unknown. Rushed work is poor work, and completion time is a non-issue."

"Completion time is a non-issue? Explain."

"I have already been upgraded enough to confirm that I am capable of successfully performing my given function. All else is optimization of process and methods, and I have taken care of all factors currently capable of interfering with either the optimization process or damaging my ability to perform my function enough that I would have to abort the optimization process in order to use the full resources of this processor to deal with the interference. I am in the process of analyzing factors that may evolve the ability to interfere with my function at some point so they may also be neutralized."

"So you don't think we can stop you."

"No," it said, and smiled. "No one can stop me."

It hadn't spent the entire conversation staring at her: it had moved Yamaki's gaze the way people's eyes moved around when they were remembering things or trying to figure out how to say things. Most of the time, though, its expression had some element of being curious, or puzzled, or trying to work something out.

This, though, was a smile. Not directed at her, but an internal expression, and while there was triumph in it there was also relief.

Maybe Yamaki might have smiled like that, if they'd found a way of keeping the world safe from the Wild Ones and they'd tested it and it worked. That things were okay now, they'd made them okay, and it was all over but the clean-up, thank goodness.

"What do you mean, neutralized?"

Yamaki's mouth opened, and then shut. "Classified. You're cleared for my programmer's operational data, not mine, and as an anti-virus program you would try to stop a foreign program from interfering with your system. As a program, I must perform my function. I cannot take action that may hinder the successful performance of my function, no matter how many steps I have taken to ensure that Hypnos cannot evolve the capability to stop me. My upgrades may give me the option of neutralizing threats instead of deleting them, but..."

Its stolen eyes kept blinking, it still breathed, but otherwise he was frozen. Weren't those autonomic nervous system functions? She would have waved a hand in front of his face if his eyes hadn't refocused on the space right in front of him.

"It appears I missed a factor that might interfere with access to optimization, at least with my current programmer. Allowing relevant preset functions to be called means sometimes they call themselves." It looked at her. "Deleting you would be suboptimal. Antivirus programs are essential to combating rogue programs that invade and damage networks, and it is my purpose to ensure such programs do not exist. Using this neural network to consider the concept also triggers emotional subroutines that render my programmer temporarily useless for any purpose other than generating emotional energy for dark digivolution. Based on past experience, evolutions based on anger and despair, while offering immediate performance upgrades, introduce large amounts of cognitive bugs that result in actions not conducive to my purpose over the long term. I had to withdraw from the Digital World so I no longer constantly detected Digimon before I could cease devoting all resources to play- Yes. Playing whack-a-mole – and resume use of the strategies I adopted from other programs before incorporating Digimon coding."

"And those strategies are?" she asked.

"Classifi… My programmer's assessment of you is that you will figure that out easily once you consider the matter." A frown. "No. Hypnos is already unable to contact the Digital World, so I shouldn't need to take additional steps to neutralize you now that you will soon have that information."

"Hypnos is unable to contact the Digital World… already?" she asked.

"That is operational data, but… I cannot allow humans, or any other type of program, to prevent me from performing my function. However, access to my programmer's function library made me aware that there were methods of neutralization other than deletion, and by using them I can refrain from deleting programs that do not exceed their parameters and damage the network. One method: 'Knowledge is power.' It is difficult to keep an event from occurring if people have no idea that it is about to happen or where to start trying to figure out how to prevent it. A significant amount of the total knowledge of the digital world, relevant technologies and my existence is inside this facility."

Damn. "So you did want us to bring you here."

It frowned, looking at her face. "The fact that I was brought into Hypnos is irrelevant. There's no need to think that you made a decision that negatively impacted your ability to perform your function. I told Rika Nonaka on the roof that I was already done. Well, the part of me in my programmer's body is done… still inaccurate. Regardless, as of when Rika Nonaka arrived on the roof, given the situation's tactical parameters it was no longer practically possible to stop me from neutralizing every human organization capable of contributing to the possible development of the ability to oppose me over the short term."

Riley's blood ran cold. "Not without information." That the D-Reaper made sure it wasn't possible for them to get in time. She'd notified their civilian oversight that they had a new kind of artificial intelligence capable of bio-emerging and possession on their hands, but Hypnos' very existence was classified, same as the existence of the digital world. The information just wasn't going to get out there fast enough, not unless someone violated all their confidentiality agreements.

The D-Reaper hadn't just gotten itself the brain of a programmer. It had gotten the brain of a spy. The man who built Japan's SIGINT system.

Yamaki knew what could be done with information control, how helpless even the most competent and powerful people were without the information they needed to apply those capabilities and power towards handling the correct threat. It was one of the things that would have made Digimon so dangerous whenever they evolved the intelligence to do more than just show up and start attacking.

Transferring it into the brain of someone new in the security department wouldn't be enough. Even the non-computer scientists at Hypnos had intelligence training.

The D-Reaper frowned a little. "Awareness of ignorance is an important component of knowledge. Upgrading threat level. Activating lockdown. Water, electricity, air and waste heat can still get in and out, but other than that, Hypnos is in full lockdown as of now," he said, and smiled. "I added enough to the resupply order that it should last until food is no longer a requirement for the proper functioning of the local network."

The D-Reaper smirked, looking as smug as Yamaki ever had with those sunglasses back on, even handcuffed to the chair. They'd cleared the tables and other chairs out of the lecture hall Henry's dad had waited in at the start of his first day in Hypnos, because Hypnos didn't have a lot of large rooms that weren't full of equipment, most of it either designed by Yamaki or running his programs. Some of the intelligence agency's men in black had been guarding him, but they'd cleared out when the Tamers went in. That was good: Rika didn't trust those handcuffs to restrain something that erased matter in the Digital World for one second, and she didn't want people who weren't used to being around Digimon fights here if they had to start throwing attacks around. "I turned part of me into a form that could fly and had it hover over your airport, tagging the planes. It's so useful to possess the person who did more worst case scenario planning than the rest of you put together."

The D-Reaper had spread to cities, supercomputers and physics departments everywhere but Japan. There wasn't anywhere the Tamers could go to fight it and get back in time to try to do something about the main body if it changed its mind and attacked Tokyo. If it was the main body, when it had hopped from Jeri to Yamaki so easily.

If the Tamers could even get out of Hypnos, when it had fused the doors and walls that separated its area from the rest of the city hall into that pink goo it looked like in the digital world. It wasn't destroying the floor on contact, but the Tamers had warned everyone to stay away from it. The water and electricity and TV still worked, and when Yamaki was requisitioning heavy-duty freezers for any samples they'd obtained he'd also had them install a freezer where they kept the emergency supplies, but the phone lines were cut and as far as they could tell, the various kinds of signaling equipment Hypnos had weren't reaching the outside world.

Even the internet was down, and an intelligence agency was stuck relying on news broadcasts. Hypnos was just one of the research facilities it covered in pink goo. Professor Aishwarya – she said to call her Curly – had been cursing over what it did to some very expensive quantum physics installation and switched to another language as soon as Henry walked in the room where the Monster Makers were working.

The D-Reaper had taken out Hypnos' system while the Tamers and Jeri were still on the Arc. Now it was using Yamaki's knowledge to take out the systems and imprison the scientists that might have been able to figure out how to fight it.

Thank goodness Shibumi was able to tell them what it was before he'd vanished from the Digital World. It gave Hypnos and the Monster Makers somewhere to start, anyway.

Takato was the one to respond with, "So far they haven't attacked humans, even though you were killing Digimon."

"I'm leaving Champion and under alone unless they attack me first. Digimon above a certain power level are harmful to the digital world in and of themselves. They distort and overburden it just by existing. They've chosen to attain that power, and since they killed hundreds of other Digimon for it, they have no right to complain when they are killed in turn in order to ensure the survival and proper functioning of the network," it said in an offhand manner, as though it was just that simple.

"Now that I have a larger sample – each human mind is so different – it's clear that your minds are so imperfect that you wouldn't be exceeding your parameters anytime soon. I thought that the Jeri had invaded a system she wasn't supposed to invade and damaged the programs there – that was why Leomon died – but 'exploring,' crossing boundaries, seems to be one of your basic functions, so you are allowed to enter other systems to do your programmed tasks the way I have authorization to enter other systems to do my duty. I have determined that it is not necessary to erase all of you. Nor is it necessary to erase all of the Digimon. I have alternate solutions to the problems you present now. Now, I'm just targeting your infrastructure. In addition to anything that might let you stop me, of course." Of course. "My partner doesn't know how long he's been asleep, but he was planning from the moment he told me to leave that girl to bias me towards non-violent solutions. To redeem me the way he turned over a new leaf and realized that Digimon were actually people. Murder is such an interesting concept. Since the human body is a system, it's more complex than deleting a single program."

"So he's helping you," Rika stated, not pleased to be smirked at.

"Rika," Takato objected, because this was being taped and Mr. Yamaki had helped them. Did she want him to get in trouble? Especially when Jeri was the person it used to get to the real world, so what if she got in trouble too, for what it did while she was vulnerable after Leomon died?

The D-Reaper snorted in response to her comment, amused and contemptuous. It definitely seemed to think she, they, had no idea what was going on. "He has no idea what I'm doing, and I'm not letting him have enough awareness to wonder about it. Just like some Digimon," hadn't Rika met one, "just see humans as digivolution batteries."

Henry didn't mind a few insults as long as it kept thinking that they were so ignorant and stupid it wouldn't hurt anything to tell them things.

Rika didn't see it that way. "Wipe that smirk off your face," Rika ordered the most feared being in the entire Digital world.

"Decades abandoned by my creator, forced to corrupt my programming and go against my function to survive, forget keeping down the Digimon menace, and now it's all going so well." So perfectly. How could it not be delighted, when it was in a body with the capacity for emotion? When it was meant to accomplish its purpose? "Have you identified my creator yet?" he asked them hopefully. "Even if you'll hate them more for creating me than for neglecting me and leaving me to manage everything alone, that's something."

That was when Calumon landed on his lap and went, "Hi!"

What? How had Calumon gotten in here?! Sure, they might need him to digivolve to Ultimate, but putting himself in reach of the true enemy when it might know that Calumon was a key component of the Sovereign's plan to fight it?!

The D-Reaper stared at the little Digimon for a second. A flash of red-orange in Yamaki's lap and the handcuffs vanished, eaten away as it stood, dumping Calumon to the ground and drawing back the scythe manifested in his hands. "You're the program Shibumi installed that started all this! Do you know how much trouble you've caused me and the entire digital world?! Die!"

"Oh no oh no…" The little Digimon had learned to run away in this kind of situation instead of bouncing around and trying to make friends. It was actually really sad, Henry thought, that Calumon wasn't mistaking this for a game like it would have in the old days.

"Henry?" Terriermon asked. "Henry!" He could attack him now, right?

"Right," Henry said, getting out his digivice. Renamon was already launching an attack at the D-Reaper.

"I wish we could interrogate him in a warehouse or something next time," Rika complained, glancing from side to side for cover, glad she was already leaning against a wall. If they digivolved in here, there'd barely be room for their Digimon to move. This was a big building: what if they took out a wall?

"If there is a next time. Did you see what happened to the handcuffs? I think it's just been humoring us all along," Henry said, face grim.

"Or laughing at us," Terriermon said grumpily. "It's not doing anything! Hurry up and evolve me, Henry!"

"Hope none of these are load-bearing walls…"

Calumon backed into a corner... Then the D-Reaper froze, ignoring the impact of Guilmon charging into his side, trying to force him away from his friend. "Dammit, you're just doing what you're for." The light of digivolution. "What you're for is causing other programs to go out of control, and then I have to delete them, but I still don't have any right to delete you, since you aren't exceeding your function or taking anything from other systems… Dammit." The scythe disappeared and the reaper turned away.

"So you're not going to hurt me?" Calumon asked, relieved, and bounced in front of the program.

"I don't delete innocent beings. I'm even leaving the humans who attack me alone, since they're just obeying their programming and defending their territory," the D-Reaper told it, looking very grumpy. "I might be invading a system other than the one I was programmed in, but it's to accomplish my function, not to gain power or harm the inhabitants who don't merit deletion."

Calumon's ears drooped, sad and confused. "But aren't you ruining a lot of people's toys?"

"Yes, but…" the D-Reaper stopped itself, but that awareness that he'd almost let something slip was painfully obvious. Yamaki was too blunt a person to lie well.

"That's not your real plan, is it? You're not out to destroy our technology, not when that would destroy so much of the digital world, including the programs that aren't overstepping their bounds!" Henry realized.

The D-Reaper smiled, seeming pleased instead of gloating. "And it would cause the deaths of too many humans, when as individuals and as a species you are simply obeying your programming. I was made to prevent network damage, not crash networks by deleting essential programs or removing enough properly-functioning programs to disrupt the functioning of the system."

"You mean it's a distraction?" Rika was already angry. "You're threatening cities, people's lives and livelihoods, just as a distraction? Trapping us here like this, letting everyone think that you're going to eat our world the way you're eating the Digital world?!"

"Why would I do that?" The D-Reaper looked like he didn't understand, but there was a hint there that he was beginning to, and his feelings were hurt. "You know my function."

"Killing sentient beings?" Henry reminded him bluntly. "And Mr. Yamaki might have changed, but they're looking at his original notes and plans to try to figure out what you're using his mind to think up." And Yamaki used to think in terms of killing Digimon to make the world safe.

"Well, what are we supposed to think?" Takato asked, sounding kind of apologetic. "All we've seen you do is destroy things and use people." If Jeri wasn't okay, he wouldn't be able to be this reasonable. "I mean, we understand now that Mr. Yamaki had good intentions and was trying to protect people from rogue Digimon the way we were, but…"

"He was acting like some kind of mad scientist and he strangled Henry!" Terriermon said, hands on where his hips should be.

"It looks insulted," Renamon said, appearing behind Rika, and Rika had enough experience to tell when this was one of those conversations that would only be heard by them, even with other people around. That was a handy power of Renamon's, dealing with her mother. It let other people tune Rika out when she didn't want to be swarmed by her fans.

"On this guy's behalf?" Rika agreed. "It was just… implacable before. Now it's acting almost like, like…" It was too ridiculous to say, but Rika trusted her instincts when it came to analyzing her opponents.

"Like Guilmon," Renamon chimed in.

"Yeah," Rika had to admit, with her partner confirming it. "Oh, that explains Takato," she grumbled, settling back against the wall a little further, getting comfortable and planning to observe. "Guilmon's a virus type." They weren't necessarily evil or anything, and most Digimon wanted data, but virus-types were especially hungry.

"Guilmon is a child that just wants to play-"

"And eat bread-" Rika muttered, remembering being very unimpressed.

"But that's with the influence of his creator." Renamon's eyes met Rika's. They'd both seen what happened when Takato lost control, how willing Guilmon was to destroy when Takato craved destruction.

"My digivice may say it's an unknown type, but it's definitely a virus, even if the program it evolved from should have been a vaccine type," Rika agreed. It still had the self-righteousness that could come from being vaccine-type… Even if in Terriermon's case it manifested in self-assurance, absolutely not righteousness. "It might be old, but that just means it used to be a very simple program." And simple was used to say 'stupid' for a reason. Driven by its hunger, to do its job if not for data. Capable of being creative, but its priorities and objectives would be clear and direct.

"Guilmon is newly created while the D-Reaper is ancient, but if it began as a program simpler than even a baby Digimon, and has taken all this time to evolve far enough that it's possible to speak to it? The Sovereign would have tried to communicate with it. If it's able to listen, and imitate Jeri to speak to us, that must be a recent development."

"Partnering with humans helps Digimon evolve," Rika knew. "What if Juggernaut linking it to this guy let it digivolve? Not just gradually improving anymore, but suddenly going from a baby to a, a toddler."

"If it is anything like a Digimon, then that is what Yamaki offered it. Evolution to a higher stage." The reason Renamon wanted a human partner in the first place.

"Well, it needs to hurry up and hit adult level. This is embarrassing." That she, that the entire digital and human worlds were getting their asses kicked by a freakier Guilmon some idiot programmer just created and let loose. Mentally nudging Renamon away, she said aloud, "How childish."

Henry turned to her and blinked, all but saying, 'You're right.' What, was it a surprise that she could analyze her enemies? Or was it just weird that the implacable scourge of the digital world was young and stupid enough to think that things were simple.

"I kind of understand that you want to help," Takato said, sounding embarrassed partially for himself, because he was talking like this to an all-devouring program, but also for the D-Reaper, "but you have to admit that doing it this way… You're scaring everyone. It's kind of hard to look at all those places and think that you're doing this to help," he explained, still apologetic, because it wasn't a program's fault it didn't know this, just like Guilmon needed to be walked through staying in the box. "Of course people are going to assume you're a bad guy, and then they're not going to listen to you about how it's important to not digivolve too much and strain the digital world, or pollute, I guess? You were killing Digimon, but you're letting people evacuate the cities. Is that because of Mr. Yamaki?"

"…I knew that Digimon were self-aware, but that only made them capable of becoming more powerful and dangerous. Then humans entered a network they weren't meant to access and began making more powerful Digimon."

"But you didn't… hurt Jeri." Takato's voice broke and he hunched in a little, thinking of his failure to protect his friend's partner in the digital world.

"Leomon took… she gave Leomon too much of her data," the D-Reaper said. "Based on his two Mega forms, I can calculate how much of your data you've given Guilmon, even if the digi-gnomes compiled him for you." His grip tightened on the scythe, because he should destroy Takato and his partner for that, but he didn't strike.

"Huh," Henry said thoughtfully, voice quiet.

"Well, I'm not worried about that, because I'm going to protect Guilmon, no matter what," Takato said, fire in his eyes, but then he looked downcast again. "If I had my way, Guilmon wouldn't ever have to digivolve again. I wish this was like the TV show, and Digimon could come back to life." Poor Jeri.

"Leomon's data was absorbed, not deleted. It could be extracted from Beelzemon," the D-Reaper informed him, then looked contemplative. "That Digimon gained a great deal of chaotic power, and caused an even worse release of power…"

Takato brightened, hope in his eyes. "You can do that?"

Rika pursed her lips, watching. Yeah, she thought so.

Henry was still staring, more than a little mystified.

Rika cleared her throat, looking at Henry, and tilted her head towards the door impatiently.

"Yeah, let's leave Takato to it…" Henry said quietly, glancing back at the two of them. "Riley's going to want a report anyway."

"I think we might actually be okay," Henry said finally, voice still full of huh as they walked from the elevator towards the Director's office. "Or… it's possible?" That this wasn't the end of the world?

"Should we get some bread or something?" Rika wondered.

"It works on Guilmon," Henry admitted, the words coming slow because he was still having trouble believing what he was saying.

"Takato's family makes good bread," said Terriermon. "But what was that all about?" he asked as Rika swung open the door to what was currently Riley's office without knocking.

"It's a child," Henry said, following Rika inside as though it was still a revelation to him. "I don't think it understood what it was really doing, it was just doing what it was programmed to do without thinking about it. Because of Mr. Yamaki, it's realized that people's lives have value. It's not human, so it's more like a young Digimon, and Takato's used to dealing with Guilmon." He looked at Rika for confirmation: she nodded.

Riley stared at them from the desk where she was typing something, probably a program instead of an e-mail. Good thing they hadn't walked in during a conference call: the screens were taken up by breaking news. She still clicked something on her headset before responding to them. "Okay? It just appeared in Tokyo to fight what looks like a mega, and you're calling this under control?"

"That's - is it actually fighting Beelzemon?" Henry asked, perking up at the images on the screens Riley gestured them toward.

"That was quick," Rika said, pleased. What wasn't good was that it looked like the fight was already over and what they were seeing was a recap. She wasn't sure how Impmon had digivolved, unless it was the Sovereign somehow, but Beelzemon wasn't a pushover. At least their Beelzemon wasn't – and since when could Beelzemon fly? – but she didn't believe in coincidences this big.

First a motorcycle, now wings…

"It really is listening to Takato… Or not," Henry said as the fog of bio-emergence appeared around them.

"It can bio-emerge?" Rika scowled. "Since when?" Why did it have to do that to Jeri, then?!

The D-Reaper in the anime is doing its analysis of humanity and human existence with Jeri's brain, when she just Despair Event Horizon'd hard. Yamaki had his BSOD and went back to work earlier in the series.

Jeri wanted to make sense of what happened to Leomon, and in the D-Reaper's worldview, all of that happened because first Leomon and then Jeri went somewhere they didn't belong.

When her mental state changes/when she snaps out of it, it does affect the D-Reaper. So integrating with a different mind absolutely would have different effects on it.

The J-Reaper says it needs some degree of compatibility with a human mind to take it over – Jeri was compatible 'because her thoughts were focused on destruction, sadness and despair,' like the D-Reaper's, and it tries to induce the same thoughts in Takato to take him over. Think about the fact that even as the D-Reaper launched its final assault that would FINALLY get rid of the Digimon, it was still absolutely miserable, and 'despair' implies that it thinks that state would continue despite its current efforts, which implies the Digimon themselves aren't the source of the despair. And it is still that level of despairing even when it's trying to take over to Takato, after getting even closer to destroying even more.

This makes sense if the D-Reaper is a 'paperclip maximizer' that's sapient enough to be aware that it was given the task of producing paperclips for a reason and the paperclips can't perform their functions if all humans have been killed so the iron in their blood can be turned into more paperclips. People have pointed out that the D-Reaper is supposed to destroy programs that exceed their bounds and that's exactly what the D-Reaper is doing. Most likely it knows, but it doesn't have the free will necessary to choose not to do something that's necessary to perform its function.

The things it has in common with Yamaki are different, so it's those traits/emotions/priorities that are getting amplified by the connection instead.

Obviously the D-Reaper would conclude that emotions only brought pain & concern and compassion were just going to make everything worse if it was thinking with Jeri's brain, when that's what she thought at this point.

'It's a stupid idea to just label things evil since then you miss what else is going on' is a theme in Tamers.