Shinobu wished she could have brought Kanao for this mission, but at the same time, she didn't want her younger sister around Kamado. She wasn't even sure why. Except that he was a demon… or becoming a demon. Or perhaps the fact that his blood could turn other people into demons and just a couple of drops of his blood ate through and converted an entire liter of their precious store of demon blood in less than an hour. Closer to twenty minutes, actually. And she suspected that a circulatory blood system would speed that up to minutes.

Humans converted at a slightly slower rate, according to the tests she'd run. And each of the blood samples had had their own uniqueness, just as most of Muzan's demons did. It actually even converted animal blood, although at the slowest rate so far. The more intelligent the animal, the faster the rate of conversion. Insects and other bugs didn't convert at all. Muzan's didn't convert insects either… unless one counted demons as bugs…

That test, actually, had taken her the longest to wrap up and conclude. It was part of the reason why she'd insisted on staying behind to finish her observations.

Was it wrong to want to protect her sister from all of this? From Shinobu's own fascination with this new type of demon blood and a demon doctor who had very interesting results and conclusions of her own? She didn't protect Kanao from other Demon Slayer duties…

Or maybe it was because she actually believed Kamado… but that encouraged her to let her guard down, which would encourage Kanao to do the same… and what if they were all wrong? Was this irrational?

Sooner or later, her little sister would have to meet Kamado. Until then, though…

Shinobu sighed and looked up at the tree tops along the sides of the road. She was just getting into forest territory and would be able to travel faster. She did want to reach the Final Selection area by morning, and she'd have to stop for a mission on the way. She'd need to arrive at that city by nightfall. She was considering when she should abandon the actual road and take to the trees when a voice called out to her.

"Shinobu-san!"

Blinking, she looked ahead and saw a figure jumping through the trees she'd just considered. It took her only a moment to recognize Kamado rushing towards her and Shinazugawa just behind him. Something about that struck Shinobu as odd… The younger Hashira looked so relieved for a moment, and then, to her surprise, he stopped; simply froze in mid-step on a tree, still a fair distance away. Then he turned to face Shinazugawa. She couldn't hear their conversation, but simply continued to approach them as the Wind Pillar glared angrily at Kamado. Eventually, he very reluctantly sat down on a larger tree branch. The Sun Pillar nodded as if satisfied and then turned to rush over to Shinobu.

It bothered her that Shinazugawa turned his face towards her and just stared. She couldn't tell if he was blinking, but she didn't think so…

Kamado landed on the road in front of her, looking so relieved again he immediately bent over and put his hands on his knees, breathing hard. Not that hard, though… and his pants had been sliced in very strange places. As had both his Haori sleeve and his demon slayer outfit's sleeve on one arm.

She could also swear she'd seen glowing red eyes, not his normal burgundy…

"Kamado-san," she said, closing her eyes and smiling wide. "Wasn't I supposed to meet you at Mount Fukujikasane? And what, exactly, is wrong with Shinazugawa-san?"

He actually winced at that, his hanafuda earrings clattering against his cheeks. And then he looked up and Shinobu's eyes narrowed.

"Kamado-san, is that kanji written in your eyes?"

He sighed. "Yes. It's… a holdover from my previous lives, much like the demon transformation."

"Hmm. A Waxing Moon?" She may or may not have sounded rather accusatory at that.

The boy shuffled, looking down and kicking the ground with his bare feet. His bare, clawed feet. "It's not like I had a choice…"

His previous arguments about how most demons didn't choose to become flesh-eating monsters made a great deal more sense with that point.

"Hmm," she responded. "Does Oyakata-sama know?"

This time he stared her right in the eyes (as terrifying as she found that) and nodded firmly. "I've told him more or less everything.

"I see."

This both explained so much and brought to light even more questions. Why had his cells mutated as they had? Was that partially due to his Demon Blood Art? Living so many lives? Being turned so many times? Becoming a Waxing Moon… Or was there more to it?

She rather suspected the latter.

For several seconds, she studied him, looking for any sign of smugness, superiority or even just amusement, but she found only determination and perhaps guilt.

Then she glanced back up at Shinazugawa. He hadn't moved from his spot, and he hadn't stopped staring at her.

"And Shinazugawa-san?"

Another flinch and the boy looked down again.

"I don't know how, or why, but… we ran into Waxing One, Kokushibo. He ambushed us just after my first attempt at cleansing a demon. He—"

"How did it go?" she interrupted. She always had been too curious for her own good. "The cleansing, I mean."

The boy blinked. "Um…" and then he deflated. "I managed to burn the demonic cells out of him but… he died. I tried to save him, even tried to breathe for him like Tamayo-san taught me but…"

Shinobu frowned. "He died… but didn't disintegrate?"

Kamado stiffened a little, but nodded. "His body didn't have any demonic traits that I could see but…" he paused and winced again, "Shinobu-san, it's like torture to them. At least slicing necks is fast and relatively painless. I… I don't know if I can do that again."

She put one hand on her hip and the other cupped her chin as she thought. Should she believe him?

"Can Shinazugawa-san confirm this?"

And there was that wince yet again.

"Not… right now."

She frowned. "Please continue explaining then?"

"Yeah," he muttered. "The demon's shrieks were… very loud. I'm pretty sure that's what attracted Kokushibo." He shook his head. "I told Shinazugawa-san to stay out of the fight, and when it became clear that I would not likely win, I told him to run."

Shinobu knew exactly what reaction that would bring.

"He didn't, did he," she said facetiously. It wasn't a question. Kamado still answered it with a shake of his head.

"The Waxing First… he's terrifying. I've never had to seriously fight him, not since I got the ability to become a Waxing Moon myself. It only happened twice in the loops – twice too many – but he could actively kill demons – or absorb them – so very few demons actually tried to fight him for his position."

"Then how did you gain your rank?"

Kamado's jaw clenched, as did his hands, and his eyes grew hard. "My rank was never meant to recognize power. Muzan wanted me to overcome the sun for him. That was the only reason he set me apart…"

Yeah, that sounded less than pleasant… to say the least. She didn't let her sympathy blind her, though.

"Did you?" she asked.

He blinked. "Did I what?"

"Conquer the sun for him?"

The steely gaze returned – frightening with his new eye color and kanji. "No. Never. No matter what he tried."

That… could go some very dark places. She contemplated pushing him, but ultimately decided not to as this was not the best place or time for such conversations.

"And Shinazugawa-san?"

Kamado rubbed the back of his head uncomfortably. "When I fought… well… I can beat Douma. It isn't an easy fight, but I can do it. I thought I'd stand a chance against One but… this time, I fought Kokushibo… and lost." He held up his tattered sleeve and then gestured to his equally ruined pants. "I managed to keep my sword, but… well, Shinazugawa-san… he stepped in between us to give me time to regenerate. I'm not the best at regeneration… It's something I'll have to work on. Maybe Akatsugi can help me. He regenerates almost instantly."

He looked up with a hopeful, almost excited smile at Shinobu, but it faded when he saw her unimpressed expression.

"Uh, right. Waxing One got past Shinazugawa-san and tried to kill me again. I still had my sword, like I said, but that only stalled him. Shinazugawa-san got a hit on him because he was distracted with me. It sliced off his arm and he… um… cut Shinazugawa-san in half in retaliation."

Shinobu's eyes went wide and her breath hitched, but then she looked back up at the figure in the tree. If he was…

And then she put it together. Kamado's reluctance and his state and Shinazugawa and…

Oh.

Oh.

"You… turned him into a demon."

"I couldn't just let him die!" Kamado exclaimed, but then he sighed again. "I actually expected him to be like Akaza… er… Akatsugi. Thought he'd be, you know, his normal self but with weird cravings and fangs."

"I take it that isn't the case?" Shinobu asked, eyeing Shinazugawa warily.

Kamado shook his head, suddenly looking so, so tired. "He can't even talk yet, although he seems to understand me. Just like Nezuko…" He cut off and closed his eyes for a moment as if to gather himself. Then he turned his red gaze back on her again. "He needs to sleep. He needs a quiet, safe place… and um… I kind of do too."

She frowned and looked up at the distant white and black-clad figure staring at her still. Knowing the truth made his actions both more and less creepy.

"That puts me in a difficult position," she said with a sigh of her own. "I also have a mission I need to accomplish, so I cannot escort you back to the Ubuyashiki estate. I'm also not… entirely comfortable letting two demons go off on their own."

He looked a little green and ducked his head. Not denying it, then. So, did that mean his transformation was complete? Or had he simply recognized his denial? She supposed it didn't matter at this point.

"Although," she said, her eyes a little softer, "I am glad you came back on your own. That is a point in your favor."

Kamado smiled wanly up at her. "Thank you, Shinobu-san." But then his grin fell. "Although Genya's going to kill me."

"Hmm," she said, only having met Shinazugawa Genya once. Honestly, she could believe he'd try. Of course… "That's if Shinazugawa-san doesn't regain himself and kill you first."

This time the demon groaned and let his face fall into his hands. Thus he didn't see Shinobu cover her mouth with her hand.

"He's not going to understand, is he."

She smiled – genuine for once, if a little pitying. "I don't think so. In any case, shall we go?"

He sighed and nodded, letting his hands drop back to his sides. "Yeah. Let's go… but I'll have to keep Shinazugawa-san back. I… don't think he's trustworthy around humans yet."

"I assume you haven't let him eat any human flesh?"

The boy shook his head emphatically. "No! I've kept him away from towns and travelers as best I can."

"So you have the same kind of control over him that you have over Akatsugi?" she asked as she began walking towards Shinazugawa's tree.

He hesitated. "Yeah," he finally answered, subdued. "Not complete control, thank the kami, but definitely enough to make him stay in that tree or… not attack you."

"Oh, I can take care of myself if he misbehaves," she said, widening her smile again, half because it was true, half in warning.

Kamado, surprisingly, smiled right back (and it was still too real…). "I know you can, Shinobu-san. I was more worried that he would die more than you. I saved him and, I guess he's one of mine now… that means it falls to me to protect him!"

She honestly couldn't tell whether he was joking or not…

Somehow, she leaned towards 'not'.

Whether he was lying and playing them all or not, this boy truly was amazing.

"Shinazugawa-san," Kamado said as he and Shinobu reached the tree he was perched in. He had gotten onto all fours and was peering at her, drool dribbling down from his mouth along with his very large, long, purple tongue…

Yeah, she would stay away from those implications. Down that path lay madness.

"This is Kocho Shinobu-san. I know you are hungry, but you are not allowed to eat her. Am I clear?"

The new demon with his bright purple, slitted eyes, snarled at them.

Kamado just shook his head, smiling. "Nope. If you try, I will stop you. But soon we'll get to a safe place and you can rest, okay?" All that met his words was a rumbling growl. Somehow, that struck Shinobu as still very much like Shinazugawa.

"Come on. We're going to follow her and make sure she stays safe, okay?"

The grumbling growl stopped.

"Okay!" Kamado said brightly then turned to Shinobu. "Your lead, Shinobu-san."

Well, this would be an interesting trip.

xXx

"Kamado-san," Shinobu said brightly, making sure to keep one eye on Shinazugawa as they traveled. He hadn't approached her, but he also hadn't stopped staring at her. It was getting unnerving.

"Yes, Shinobu-san?"

"Do you think we could continue experimenting with your Blood Art once we reach the village – assuming, of course, that there is a demon behind the disappearances in the town."

She expected an immediate answer of either yes or no, and managed a glance at him when she received neither before returning her gaze to the (former?) Wind Pillar. He looked troubled.

"I… don't know, Shinobu-san. I know they're demons but… I am too… now," he sounded so dejected. Not that she blamed him. "My Blood Art hurts them. Badly. I don't want to torture them if I don't have to."

"Hmm," she responded thoughtfully. Then she smiled again. "Did you forget that I am a doctor who specializes in substances that affect demons?"

He blinked at her, then frowned as if he was trying to put that together. She sighed inwardly. "What if I told you I had a poison that could render them unconscious?"

If he answered no, then he was either traumatized or playing them. If he answered yes, though…

"You do?! That would be great! I mean, you just have to make sure they don't see me and that they're knocked out. I think the pain the previous demon went through was part of the reason they died afterwards. But if I can save them…"

"If you can save them, then I will gladly help in any way I can, Kamado-san." Even though she knew he couldn't see her, she still smiled at him. Shinazugawa growled at her. She just shot him an unimpressed expression and pointedly kept her hand on her blade. If he so much as twitched wrong, she'd slap so much poison in him, he'd be dead before he hit the ground…

Even if she really didn't want to do that to him. She'd known him almost since she'd first join the Corps.

After several moments of companionable silence, she spoke again. "I'm surprised he can go into the sun."

"Yeah," Kamado replied. "I mean, everything else about him is just like a newly turned demon, but I guess since I've 'conquered the sun', then so has he. "

She heard the uneasiness in his voice clearly. "You really don't like having control over them – Akatsugi and Shinazugawa, I mean."

Kamado's jaw clenched. "No. I mean… it's useful, sure… but isn't that part of the problem? I… really don't want to get used to this."

"Hmm," she replied easily. When he spoke like that, she found she could believe he'd lived almost a hundred lifetimes.

They continued in silence.

xXx

Sanemi was hungry… but he couldn't eat! And part of him didn't want to eat, but most of him wanted to eat everything

But Master wouldn't let them eat. It was bad to eat people, he said. So the new lady (who looked so familiar… why did she look so familiar?) wasn't food either, despite how good she smelled.

Not as good as that smell from earlier, but still good.

And how there were a lot of other scents of other people, but he couldn't eat them either.

"I will head into the city, then, Kamado-san," the new lady – Kocho? Yes, that was her name, he was sure of it – said with a smile that hid knives. "I recommend that you and Shinazugawa-san stay here to avoid," she glanced over at Sanemi, "temptation."

Master also looked over at Sanemi – as if he were a child he needed to watch over, which was ridiculous! Sanemi could take care of himself. He was sure of it.

"Yeah. Good luck. I might wander around the outskirts if we get restless." He smiled at Sanemi and somehow that just made him want to scowl more.

The tasty-smelling lady frowned. (It suited her face more than that fake smile.) "Be careful, Kamado-san. The disappearances in the town seem to happen in certain places near water."

"So, a water-based demon," Master nodded. "We'll be vigilant. And if we come across the demon, we'll take care of them!"

The woman smiled. It didn't seem so… angry this time. She handed over some cloth to Master – something they'd discussed before? Sanemi couldn't remember… it was hard to remember. Except he could, if he really tried, but he was more focused on how hungry he was.

"I'm trusting you, Kamado-san," the woman said, then turned to leave them.

"I appreciate it! I won't let you down!" Master yelled after her. Then he put the cloth over his hair, tied it, and took off his earrings. He also took off his haori. It still smelled kind of good from that smell of that delicious blood last night, but…

Then he turned to Sanemi. "I'm going to look a little weird, but if I roll my sleeves and pants legs up, it'll hide the slashes and cuts so I'll be less recognizable, in case the demon sees me." Then he studied the newly turned demon with a frown. "Can you take off your haori, Shinazugawa-san? It's kind of recognizable and I don't want Muzan to know you're still alive if we can help it.

"If you're comfortable with it, maybe take off your shirt? Er… what's left of it?"

Sanemi didn't want to, but Master sounded reasonable… so, grudgingly, he did take off his haori. It wasn't long because he didn't like it flapping in the wind, so he'd always rolled it up.

For some reason, that thought flitted through his mind and then vanished again, leaving only the barest echo of his dislike of flapping fabric.

Master looked him over, then shook his head. "Demons dressed as demon slayers are still going to draw attention, but hopefully less attention if we take care of it quickly. Well, Shinazugawa-san, let's go hunt some other demons."

All Sanemi heard was the word 'hunt' and he found himself grinning.

Finally he could eat!

Master sighed. "Of course that's what you'd latch on to. Then again, I remember… well, kind of, what it was like. Yeah. I don't blame you, Sanemi-san. I hope it's okay to call you that. I hate being this hungry all the time, but sleeping helps. We'll get you someplace safe soon, okay?"

Sanemi expected his anger again, but instead he found himself relaxing. Master knew and was trying to help. He was just trying to help everyone, not just Sanemi. It still didn't make him happy, but he nodded. The boy smiled and that smile practically shone like the sun.

"Would you like to lead the way then, Sanemi-san?"

Sanemi felt a wolfish grin on his face as he leapt into the trees. Master followed.

Every couple of jumps, Sanemi would stop and sniff the air. He didn't remember having a really good sense of smell, but something about the changes on the wind could tell him things. He wasn't sure how or why, so he didn't question it further. Everything he sensed, though, told him of people in the village or working in some of the fields. They were… predictable and Master said they were off limits, so he concluded they were looking for something unusual.

He didn't know how long they'd been searching, but the sun had long since set and everyone had gone back to the village for the night except for a few stragglers and some smaller humans being very energetic near one of the ponds.

Children, his mind supplied. Children playing.

Why did that make him so sad?

And then he sensed something else. Strange movement in the water, which affected the air which affected him.

He immediately took off in that direction.

"S-Sanemi-san?" Master called after him, but didn't call him back, so Sanemi went on. He sensed Master following.

Then he heard Master say, "Oh."

Sanemi kept heading towards the children, who had all stopped. Sanemi came into view and saw a beautiful, glowing woman standing on the lake… floating towards them, actually, just above the water. She held her hands out to her sides peacefully, but Sanemi could sense her blood lust.

That was what they'd come here to hunt.

He grinned, paused on one particular tree, knowing instinctively just the right angle, and launched himself forward, across the water, colliding with the woman and sending both of them screeching into the shallow part of the pond filled with reeds. He heard the children scream behind him but couldn't bring himself to care. Master would handle that. He wanted his hunt.

"What are you doing?!" the woman, no longer glowing or floating, shrieked at him. She had yellow-gray skin that dripped with water and angry, snake-yellow eyes. "This is my hunting area!"

Sanemi just grinned and pounced on her. This would be fun.

xXx

Tanjiro reached the pond just in time to see Sanemi-san attack what looked like a glowing apparition. The children – teenagers his age or younger – all started shrieking. The time-traveler sighed, but quickly hopped through the reedy grass over to the group.

"Those are demons," he said breathlessly as he entered the clearing.

"W—what?" one of the children, an older boy, asked shakily.

"You need to leave," Tanjiro insisted. "In case she escapes."

"S-she?" another child – an older girl – asked.

"What's wrong with your eyes?" yet another girl asked fearfully. "You have kanji written in your eyes!"

"And they glow," the first girl whispered.

Tanjiro tried not to let that get to him and smiled without showing his teeth. "It's a long story."

"But the pretty lady sounded nice," one of the younger girls suddenly piped up, hiding behind one of the older boys as she spoke.

Tanjiro shook his head. "I'm a demon slayer, and I can promise you that she was not a nice person." He bent down and looked her in the eyes. "Just because someone looks nice doesn't mean they are."

"Y-you're a demon slayer?" the first boy asked, incredulous. "But you're… younger than me!"

"I'm fourteen, actually," Tanjiro corrected him with a smile. He forgot not to show his teeth.

The boy gasped.

"Y-you're a demon too…" another boy, about Takeo's age whispered.

Tanjiro sighed and rubbed the back of his head. "Yeah. But I'm still a demon slayer too. It's… like I said, a long story. I just don't think demons eating humans is right." He was going to go on, but a shrill scream broke through the evening, causing everyone there to jump.

"Um, yeah," Tanjiro decided to hurry them out of there. "We'll take care of the demon, but you all need to go home, please."

Some of the children had already started running. The ones who remained nodded in fear and turned to follow their friends.

Once they were out of view, Tanjiro jumped over the tall reeds and grass towards where he heard the fight going on.

"How dare you! I'll destroy you!" the water demon – who now looked more like she'd drowned than like she'd been turned into a demon – shrieked at Sanemi-san.

Sanemi-san who had… blood around his mouth? Tanjiro's blood ran cold.

The time-traveler watched carefully as Sanemi-san dove for the woman again, going for her neck – as he should – but with his claws. He hadn't even drawn his sword. Oh, wait… he didn't have his sword. Tanjiro hadn't had time to grab that and the rest of Sanemi-san's body. They'd have to fix that. Maybe once he could speak again?

The woman shrieked again and Tanjiro drew his own sword, waiting for the moment he knew Sanemi-san wouldn't be in the way.

Then he remembered Shinobu-san's desire to test his fire ability more and paused.

The woman stood, half in anger, half in fear as she held her arm, which was slowly beginning to grow back. That and her neck.

"What even are you, savage?!" she hissed. Sanemi-san hadn't seemed any more savage than any other demon to him…

Puzzled, Tanjiro looked over at Sanemi-san and gasped. He… had an arm in his mouth, the same one the woman was growing back.

"Sanemi-san," Tanjiro whispered.

Well, that explained the blood.

xXx

OMAKE: Tanjiro's hidden demon art: HEAD TRAUMA – Idea from CALIC0 (Not Canon)

Kokushibo's sword came for Tanjiro's neck and he couldn't block it this time. He was still regrowing his limbs (why were they growing so slowly?!) so he had limited options.

It seemed he would have to use that.

"Demon Blood Art: HEAD BUTT OF DOOM!" he yelled as he thrust his head down. It worked, getting in the way of Kokushibo's blade.

"That won't w—" Waxing One started, but cut off with a strangled sound. Shinazugawa stared with a dropped jaw… was it really that big of a deal. So Kokushibo's blade had split in half. It wouldn't be the first time he'd had to utilize that technique in his time loops.

The demon jumped back, just staring at his blade as it regrew and then looked over at Tanjiro as his limbs finished growing. He shot to his feet and took another stance.

Thanks, Mom, he thought to himself with a smile.

That was when Shinazugawa once again drew attention to himself.

"What."

xXx

AN: Thanks to Quathis, TimeLordTim and Found for their help on this!

Discord: discord. gg/xDDz3gqWfy (No spaces)