There's an old adage about how one shouldn't bother reinventing the wheel.

To some extent, those who apply it have a point. You shouldn't bother fixing what isn't broken. If it works, it works, it's as simple as that. Beyond that truism, though, there were other considerations to be made. Just as a hypothetical example, if someone had a working gasoline-fueled engine powering a car and another car which was powered by an electric motor, well...

Provided both are functional, you have two machines which, functionally, do the same thing to roughly equal degrees.

One of them doesn't need a specific kind of fuel, though.

What I'm getting at is that, instead of just duplicating entire lines of technology by rote, which is usually vastly easier, sometimes it's actually more advantageous to reinvent the proverbial wheel.

I placed the last of thirty-three blocks on my workstation and slowly powered down my matter printer. The new version I'd constructed in the wake of my promise to Kokoro was a much more complex device, able to print more complicated materials than the original. I wasn't quite to the point where I could simply fabricate entire smartphones or even microchips, but at this point alloyed metals and a variety of simple compounds were possible instead of being limited to pure elements.

"Ah, sir, may I ask a question?" Sai's voice called over my shoulder.

"Go ahead," I responded, still inspecting each individual block for signs of contamination. I was pretty sure I'd weeded out all of the problems in previous material runs, but it never hurt to be too careful, especially with where these were going.

"Hokage-sama and Uchiha-taicho had expressed interest in a wider use of the device you use to create materials from nothing. I was wondering if you had a potential schedule I could brief them on during my next meeting." At the edge of my range of hearing, I could sense the quick and easy noise of ink being applied to paper as Sai spoke.

"Unfortunately, there is no such schedule." My statement drew a halt to the background noise. "The machine requires a specific chakra mixture that can't be easily duplicated. Even if it did not, teaching someone how to use it would be extremely time-consuming and require at the very least months of preparatory education to understand the necessary concepts. Honestly, at this stage, I could almost do this by hand faster and more easily than using the machine."

Sai was quiet for a moment. "I had thought the concept of constructing a machine to do labor for you was to make tasks faster and easier."

"It's also to make them more consistent," I stated, reaching over to a well-worn set of medical documents and pulling them free. "While no two or more tools will ever be exactly the same, mechanization cuts down on the various small errors one could make in the creation process. On a similar note, the printer also cuts down on the stress I endure on a personal level while managing the process, allowing me to more readily accomplish other tasks instead of devoting all of my time and energy to resource manufacture for long periods."

"Ah, I understand. Thank you for the clarification, sir." He paused. "How long would it take you to train one or more individuals in the creation, operation, and maintenance of such a machine, out of curiosity?"

There's no such thing as 'out of curiosity' for a ninja, Sai. We both know that.

I hummed in thought, considering the question. It was obvious that Itachi and Hiruzen were fishing for answers on a few of my more powerful projects. They were at least being moderately polite about it, though.

Let's see... basic knowledge of physics, chemistry, advanced tutoring on sealing, they'd need to understand at least primitive mechanical computers, then I'd need to teach them how to create Six Paths Sage Chakra, if they could even do it...

Goddamn, I am cheating hax bullshit. OP, plz no nerf.

"Ten years," I guessed somewhat arbitrarily. "That's an estimation, though. It would depend on intelligence, motivation, whether or not they needed time for missions, chakra compatibility... a lot of other things."

Sai made a wordless noise of thought and I knew the conversation was over.

I cocked my head and held up the first block as I took a deep breath and concentrated.

The first iteration of my full-body seals had been a series of temporary applications to test the concept out. As they had functioned well enough in removing the strain of pulling two balls of potential from beyond the material plane into myself, I'd gone ahead with the second iteration. Those were the seals I'd applied during that fateful meeting with my daughter. These had worked more or less perfectly for the purpose they'd been designed for, but...

In the past few months, I'd decided to move forward with designing and implementing the third iteration of my sealing network. Although I hadn't been able to create a new system to allow me to draw even more knowledge from the Pure World, I'd added a bit more functionality to the previous design.

I tapped into one of a dozen chakra pools I had anchored to my body, releasing the stored earth-natured chakra in a controlled flow towards my hands. A second later fire-natured chakra joined the earth, the tiny particles of soil around my fingers erupting into a liquid molten fire that coated my hands and dropped tiny pools of quick-cooling lava onto my reinforced desk. I'd tried using a mixture of lightning and fire to create plasma in order to do this more 'cleanly,' but that particular advanced chakra mixture had ended up doing weird things to the magnetic properties of the materials I was working with.

Looking at the notes I'd opened from their position safely away from the heat of my hands, I fixed the design of the first vertebrae in my mind and picked up the first block of my special alloy.

First, I'd need to mold each of them into the proper shape. Then I'd have to start etching the control seals. After that, I'd need to look over the control matrix's script again. A full cybernetic interface was only meant to plug into someone's mind, after all. I needed something a bit more creative to plug into a user's soul. Once I'd checked the control matrix, then I'd start final assembly with the partial artificial nervous system I was installing.

I'd had the idea to make a replacement spine for Uzumaki Kushina the month before meeting Kokoro as a simple way to make someone's life better and tie a politically-powerful clan closer to me. It had become something of a challenge after looking through the woman's medical files and seeing exactly how mutilated her chakra network was in addition to multiple parts of her spine being completely pulverized. Honestly, it was likely only her Uzumaki lineage that was keeping her alive at this point, much less in moderately good health.

In short, there was no healing what wasn't there anymore.

Which was probably why Tsunade had left copious notes to that effect at the end of the medical report. Granted, she'd put the entire thing in much more technical terms, but it amounted to the same thing. To get Kushina fully-functional again, someone would effectively have to rebuild five vertebrae from scratch, figure out how to reconnect the series of nerves running through them, and then partially-rebuild two of her chakra gates that were heavily damaged from having the goddamn nine-tails rip its way out of her. Putting aside, of course, all of the muscle atrophy and secondary medical conditions caused by long-term disuse of her lower body. Even being an Uzumaki couldn't negate everything.

I set the artificial vertebrae down on a cooling tile and tapped each of my fingers free of residual ash and molten earth as I slowly cut the chakra feed to my hands.

One down, thirty-two to go.

I looked at the clock, confirming what I already knew, and sighed. "Okay, I have just enough time to at least pick out what's going... Sai, if you happen to be over at the tower later, remind Itachi he's expected at dinner tonight."

"Yes, sir." Sai replied with the instant reflex of a soldier accepting an order.

Which means he's going to make a special trip to accomplish a polite favor I asked him for instead of acknowledging he's not going to be over there. Ugh, maybe I should have another 'How to Human' seminar...

I shook my head and started grabbing various prosthetics I'd put together in the past few months. None of them were on the same level as what I was building for Kushina, but that was actually a very good thing. The simplified designs would make them easier to reverse-engineer for people who weren't me, which would also make it possible to do limited mass-production on a reasonable scale. It also didn't hurt that a lot of them were built on the principles of ninja-puppetry and while Konoha wasn't exactly well-known for its puppet users, they did exist outside of Suna.

Of course, I'd also need to do a proper write up of everything and didn't quite have time for that now, but I could at least sift through the dozens of different designs I'd kludged together.

…

As someone who wasn't immediate family, I'd declined offers to show up at the academy itself to congratulate the graduates. Instead, I'd accepted a mutual invitation by all involved parties to show up at the Uzumaki clan head's house for a joint party for Naruko, Yakumo, and Satsuki. Tenten had also been invited, of course, but Team Guy was out on a mission for another day or two. Our little 'study group' had rectified that by resolving to meet up sometime during the post-graduate off-week to have our own little party.

Before I showed myself at the main party, though, I had one quick errand to run.

Approaching from behind, I was happy to see he'd finally internalized the training and didn't immediately turn to greet me. Instead, the pink-haired boy made a casual turn at a nearby stall and into one of the more sparsely-trafficked tree-lined alleyways.

Even if I hate ninja games, I can acknowledge that being a ninja means you have to be proficient in them.

One of the big rules was that shinobi didn't conduct business or have important conversations in the middle of a busy street. Well, not unless youwantedsomeone to overhear you, but that was a rabbit hole I didn't want to go down at the moment.

"Congratulations," I offered with a nod.

Sakurai swallowed and nodded, smiling at me as he turned and bowed, his new headband glinting in the afternoon light as he wore it like a hairband. "Thank you sensei, I couldn't have done it without you."

I hummed, then decided not to inflate his ego unnecessarily. "You'd still have passed without me." I paused for effect as his chest swelled slightly. "Probably." His shoulders slumped. "But you wouldn't have made the overall top five."

He shook his head in agreement. "I think I surprised everyone last week when I beat Kiba." Sakurai stopped, then frowned. "Wait, how did you know I made the top five already?"

"As a general graduation present," I replied, blatantly changing the topic, but doing so in a way that promised material compensation, "I forged you a set of surgical tools and splurged for one of the better counter-agent and medical kits on the market."

Green eyes widened significantly at the scroll that landed in his hands a moment later. "Th-thank you, sensei!"

I waved him off. "Yeah, yeah. Anyway, bonus present for upping your ranking." I pulled out a small booklet, only fifty pages or so, that I'd penned in the last week after he'd taken Kiba down. "This is a reference manual for medical sealing. I've already taught you the basics, so you should be able to handle the rest yourself." I held out the document, but didn't release it when he went to take it, meeting his eyes instead. "I've already filed a copy of this with the village. It's going to be restricted to chunin and above, and only medical specialists at that. You have special permission to have this since I've been teaching you. Do not show it to anyone else. Understand?"

Sakurai rapidly bobbed his head up and down. "Yes, sensei! I'll be careful with it, sensei!"

I gave him a single nod in response. "Good." Pausing, I sighed. "Make it through the medic course in three months and I'll write you up another set of notes, maybe even teach you a few tricks if you impress me."

Sakurai brightened further. "I'll do my best, sensei! Shannaro!"

"Do that, sure, whatever." I shook my head and turned. "Now go see your blond Yamanaka princess and keep being a useless simp."

Sakurai visibly deflated. "Please stop calling me that, Kotaro-sensei."

I turned fully to meet his eyes. "No."

Then I vanished in a burst of supernatural speed before he could get a word in.