Konoha did have semi public libraries for their respective ranks and that is where Shisui Uchicha could be found for the next six months. If he was not there, he would either do his daily training or be inside one of the Uchiha's private knowledge reserves, doing the same as in the public ones.
He started relearning everything from his school days, what he had missed due to war time protocols and then, he started reading anything which even remotely interested him. The reason for that was simple. He lacked a lot of common knowledge due his his cut short education and even though he had many ideas of what he could or should do, many of those would be a lot easier if he had the basic knowledge needed for it.
History, maths, physics were completed first. Maths and physics were just plain boring, as he could do most of those things on instinct already, but it was still important to learn the real calculations and applications behind it. History instead was discarded after the first 9 books, due to a simple sad truth. History was written by the victors or by the governing/ruling body of a city or even country. While still not completely useless, it held no benefit for his current goal.
Though maths and physics were not the most profitable either, he still crammed anything he could find on those topics, until his knowledge base was on par with the fire countries top scholars, though none was any wiser to this. Anyone who heard that he learned all that in less than a month would not believe him either way and he was just fine with it.
His practical application lagged a bit behind, as he did not practice most of what he had learned, though he would rapidly assimilate that knowledge while training, as he could draw tangents between even the most complicated topics to real world examples.
Basically, he just calculated every single thing in his surroundings, his movements, others movements and more until he had such a good grasp on even the most complicated issues.
While doing that, he also studied languages or more specifically the dialects of the single language he needs to be concerned with, so that he could deduce peoples background more easily. He also read up on body language, though those were scarce and most ninja were proficient in faking it to at least some degree, which meant that it was nearly useless most of the time.
Both of those disciplines were practiced while taking a walk through Konoha, as even after the war there were a lot of foreigners. Even during the war those merchants, opportunists or mercenaries still visited all their different stops, as the civilian population was mostly spared those horrific experiences.
Some cities, villages or people did not even know that there was a war until it was already over, as the primary form of fighting this war were assassinations and standoffs in already desolate regions. This consequently meant, that Konoha was still a busy bright city on the surface, though the undercurrent of politics and intrigue were still there, though those did not need a war to fester but would always lead to some type of conflict Shisui did not want to be a part of.
Studying others language and consequently cultures proved to be a relaxing alternative to the regular training, though those peaceful walks trough the village were more of a rarity after the first few times, as he had already improved his observation skills by quite a large margin.
After 3 months Shisui had finally worked through most basic topics and could finally start with something he eagerly awaited, something he rewarded himself with. Reading up on chakra, jutsu, fighting techniques and most importantly seals, though those were left for last.
So he studied. Kneading and controlling chakra, affinities, fighting styles, weapons, weapon styles, footwork and more. He even reread everything concerning physical, mental and chakra exercies.
He found many topics of interest, starting with puppeteers threads, kunai shadow clone techniques, shadow clones themselves, genjutsu, chakra scalpels and more, but he forced himself to first lay the foundation before once again diving into his unconventional style of training.
After a long 3 more months he had finally finished all of his self set goals and stopped restricting himself to only theoretical learning. He still visited the different libraries, bookstores and similar, but he no longer lived there.
One of the reasons for that was, that he had abused the goodwill of his clan's sponsorship for such endevours long enough, while the other was simple. Practice made perfect and all the theory would be near useless without it.
So he once again started training, though his perspective had changed a lot since the last time. He found minuscule mistakes in all of his exercises, combined some of them, perfected others, completely stopped doing some altogether and re-/created and learned some others due to his observations. The first week was spent of perfecting his new workout routine, before finally he had condensed it down so much, that he had even specific settings on his weights for each and every one of them, which lessened the time he spent on physical exercises by 30 percent.
Afterwards he returned to only one set of his new workout routine a day, before starting on footworks. Originally he really wanted to focus on chakra, but he suppressed that, as footwork was more important than chakra control, as that would be another tiring subject, which would devour a lot of his time with less than excellent returns.
As he had already theorized on the battlefield, there was a footwork to create afterimages through sheer speed and technique alone, though even Konoha's library did only mention it in passing without any instructions.
Instructions for a myriad of different footworks were available though, so he learned, tested and perfected any single on of them. Some focused on stability, others on speed, strength, endurance, feints, specific weapon usages, specific weapon techniques and even more obscure topics like chakra strengthening, jutsu usage of any and all types imaginable, even extinct kekkei genkai.
He practiced every single one of those he could get his hands on, working out their advantages, disadvantages and kinks in imaginary battles, where he limited himself to only use footwork with the most basic of weapons, while creating a whole simulation of a battlefield in his head, dancing to the symphony of imaginary death.
It always started slow, his stance sloppy, but once he was able to move to a tact no one but him knew, it was refined at a near impossible speed. The starting time until that point got longer and longer though, as he practiced all those footworks into his instincts, every new one needing him to fight against all the other ones he had memories to a t.
Suddenly, he was finished and just looked dumbly for a second, before a manic grin formed on his face. Not because he had found a way to his original goal, no. He had a new idea, a better idea. He would not recreate or just learn any style that suited his singular purpose, he would incorporate all of these into his very own footwork, merging them seamlessly, while still making it possible to integrate new footworks into his own one.
That day, he started a slow and deliberate dance, boiling down each and any of those footworks to their barest form, smothering his instincts to the level he needed. He entered a state of enlightenment, solely focused on that singular aspiration. And then, after he had iterated dozens of times between all the footworks he knew, he stilled, before sinking into a stance most would find familiar but ultimately alien to their own.
Then, he danced a beautiful dance of death in his own isolated little world, cutting down his enemies using the simplest of weapons, effortlessly ending all the specters of others he could replicate near perfectly due to his sharingan's powers. That day, a speedy reaper was born and the forest was marred by the scars of his battle.
Then, after he had achieved his goal of perfecting his very own footwork, he returned to his initial stance, stilling, before fainting on the spot. His body did not even have the strength left, standing upright until he woke up from his more than deserving rest after continuous exertion for close to a week.
Suddenly, he woke up again, tripping over his aching feet, before his face hit the ground during his still ongoing stupor, before he started laughing again, realizing what he had created during this time.
If he was not already a monster, he would have earned that delegation after this achievement. He still had not achieved what he set out to do but before continuing that, he first needed a good long wash in a warm tub of water, followed by a long rest, nutritious and watery intakes and well, most importantly, he needed new custom made shoes, as his current ones vanished into near nonexistence in these days.
So the moron in question did just that, before going out again, barefooted, to find one of the ninja stores specialized on shoes. Once there, he spent an ungodly amount of money to buy possibly the best shoes on the continent. They were as light and thin as hair, sat seamlessly on his foot with no way of loosing them, were self cleaning and even had a slight repairing seal on them, coupled with their immense durability.
They still would not do anything against anything else than the terrain, but as long as he was just moving, even at the speed of sound he would not be able to break them permanently. Well that was what the salesman pitched at least and their reputation as one of the best shoemakers in Konoha heavily underlined that statement.
On that trip he had also met a few familiar faces, though they just nodded at each other in passing before going along their own ways. Once he was back at his desolate training ground, he was finally able to test out his new footwork. He had resisted using it anywhere else as he had no idea just how violent it turned out to be, as he had nearly no memory of his training, though the next few minutes showed him that he worried too much. His mind may not remember, but his body certainly did. His footwork was fluid, adaptable to any and all weapons he knew to use to at least somewhat proficiency and most importantly, through sheer accident, he created a single mirage, noticing it just out of the corner of his eyes.
He still did not push the footwork to its maximum as his training ground was just too small for that, but after that surprising discovery he started fervently training once more, though he was disappointed on the very same day, as not even two hours later he had found out how to create mirages consistently.
So he started refining it, incorporating it into his still evolving footwork, before deciding on a name for it: „Mirage's wrath".
Something he did not realize or could not realize due to his unfortunate amnesia was, that he had taken another huge step to awakening the mangekyo sharingan, unconsciously solidifying the future form his susanno would take.
Unknown to Shisui though, a yellow haired man had silently observed him during this time period, originally just waiting to make an adjustment to the previously issued weights. That man was captivated by his display and also appalled, as during that timeframe Shisui had had his weights running on their very maximum, which was the reason he was there in the first place, as his weights had a function to warn him of that, as over drafting the seals on those torture devices would lead to violent explosions.
It was a safeguard in the original design which he had still not found out how to remove as he made them for him, though he did not think that anyone he had given these two would come even close to maximum output in a while.
He did not leave, but just quietly whispered: „Monster", at which the head of his observational target snapped toward him and that thought was replaced with: „Shit, how do I explain this…"