Narrator's POV.

Riku was sitting alone in his cell, with an expression of absolute focus on his face. The bulging veins on his temples also spoke volumes of the strain he was under. A drop of water was floating in front of him. This alone would not explain his condition. However, if one looked closer one would see the drop of water stretching and bending, almost as if it was being torn apart...

Riku's POV.

"Fuck!" I couldn't suppress a groan as the headache went from barely tolerable to outright debilitating. The cause of my problems was still floating in front of me, although now it was back to looking like a smooth sphere. It's been months since I've been here, and I've been training my reishi control. Even before my incarceration, I would train my control, but due to my duties, I couldn't dedicate my full attention to it. 'The relaxed atmosphere of the Gotei 13 also didn't create a particularly strong urgency for me.'

My latest exercise had me aiming to pull a globule of water apart, instantly converting the 'water reishi' into pure free-floating atmospheric reishi. The conversion process turns out to be easy but also incredibly difficult. Reishi, as a concept, intuitively does not make much sense. With normal matter, there are distinct elementary particles and forces that, combined, do fairly predictable things.

However, reishi seems to follow the will of a conscious being. If a being wills reishi to produce a flame then the reishi will respond by becoming a flame. This can be seen when Shinigami use Hadō #31. Shakkahō, for example. However, if that is the case, then why aren't all spiritual beings with strong wills reality benders? To my knowledge, there is only one pure reality bender in the entire series.

It almost seems like, aside from atmospheric reishi and internal reiryoku, almost all spiritual beings must be given 'permission' to wield other forms of reishi.

Since reishi responds to will, why is it that the world is stable? There must be something that has set the basic rules for reishi to follow. There must be some 'great will' that tells the reishi in that drop of water to be a drop of water. It is likely that this 'great will' is also the one that gives out permission to others to manipulate reishi. 'I'm not sure the Soul King is this 'great will' since all three spiritual races existed before him, but he definitely contributes to the rules somehow. I'm definitely missing a lot of nuances, and there are probably some exceptions, but there is something to this whole permission thing.'

I know that I have more permission to manipulate reishi than the average Shinigami. I can convert reishi 'matter' into atmospheric reishi, which could be seen when in my Letzt Stil, I could break down the soil around me into usable reishi. 'However, it is proving to be extremely difficult in my base form.'

It seems like I have the permission I need from the 'great will', but I lack either the raw power, understanding or sheer will in my base form to achieve what I could in my Letzt Stil. 'If I could learn to do it in my base form, then what level of strength would I achieve in my Shikai...'

Taking a break, I started messaging my throbbing temples. Staring at the water droplet, I gained a newfound respect for physicists. This level of frustration is probably how they feel when they try to understand quantum mechanics... 'Okay, buddy, let's take this again from the top.'

Riku's POV. Year 2 in prison.

I couldn't help but break out in roaring laughter, unknowingly, my laughter contained traces of insanity. I had finally broken down the water droplet into pure reishi. I just need to upscale my fine control.

Riku's POV. Year 5 in prison.

Scaling up my control was much more difficult than I expected. The volume of solid and liquid matter increases much faster than the outside appearance suggests, meaning the amount of reishi I needed to control increased exponentially as I moved on to larger objects. But now I could break down and reconstruct a small bucket of water. The main constraint on my ability turned out to not be the amount of reishi an object has, although that contributes, but actually my understanding of what I break down or reconstruct.

I can overcome my lack of understanding of an object's structure when I break it down by using a lot of reiryoku to overcome the will that keeps the object stable. However, I can not do that when I reconstruct something. Throwing reiryoku at the problem does nothing. I must have an in-depth understanding of an object before I can attempt to construct it.

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Even then, the object I construct will be a facsimile. For example, the water bucket I constructed has unnaturally smooth sides, even when that was not my intention. Smooth to the point that water immediately slides off of it, meaning anyone will be able to tell it's fake. To be able to fool an outside observer, I would need to be extremely familiar with my construction to maybe the molecular level.

However, the cost-benefit of using this ability to reconstruct a massive domain, for instance, is likely, not high at the moment. What's the point of spending months or years thoroughly understanding the structure of a brick wall when even the weakest Hollow can break through it? Hopefully, this ability can evolve past its limitation in the future because it has immense potential.

Riku's POV. Year 7 in prison.

I was finally able to upscale my control to acceptable levels. I know that, at the very least, I can decompose anything I focus on within the range of my cell. Glancing at the cell door I correct myself, 'Maybe not everything.' Since I don't have anyone around to practice with, and I don't want to risk raising attention to myself by damaging my cell, I can't be sure if my control extends to the reiatsu of others.

The walls of my cell have traces of seals embedded in them, meaning I need to have more permission or raw power than the caster to manipulate the reishi that makes up the walls and seals. Ignoring the seals, I continued training.

Riku's POV. Year 10 in prison.

Glaring at the first kanji symbol of the seal on the prison door frame, I finally feel confident enough to start cracking it. Although my reiryoku growth has stagnated for the past ten years, I've achieved a qualitative improvement in my control. For instance, most spiritual beings lose a constant stream of reiatsu as they go on with their lives.

For Shinigami and Vasto Lordes, it's not a big problem because the loss is a tiny faction of their total. Just eating some food is enough to make up for the loss. That is not the case for Adjuchas and Gillians. Their rate of reiatsu leakage is many folds higher. Without evolving, they are doomed to lose all their reiryoku.

After so many years, I have enough control that I can permanently stop my own leakage. Meaning that no one can sense me off, just my reiatsu. Even in battle, if I so choose, my opponent will never be able to sense any changes in my reiatsu apart from the superficial. 'No more telling if I'm constructing a Kidō spell, assholes.' That, combined with my good control of surrounding reishi, will likely make me feel like my surroundings. All in all, a welcome side effect.

Catching myself before I could continue with this tangent, I couldn't help but release a mirthless chuckle. Ten years of loneliness takes a toll. Even with Sōten ni zase's company, his unique situation disallowed him from helping me fully stave off the effects of sensory deprivation. Even with a goal to strive towards, I've slipped in and out of insanity a few times. Feeling him pull slightly on my mind, I stop stalling. 'I know, buddy. I'll keep it pushing.'

Stretching out my stiff hand towards the seals, I fully concentrated on the reishi makeup of the symbols. The reishi structure was expectedly extremely complex. Sōten ni zase was analysing the structure at full speed, I also connected him to my mind to supplement the available processing power. Doing this caused me to feel extremely nauseous because the human/Shinigami mind was not meant to process information the way Sōten ni zase does. Despite the nausea, I kept my focus because this wasn't my first rodeo.

To my senses, the seals were no longer just words but complex flows of energy in even more complex patterns. To the uninitiated, seals and Kidō as a whole are just fancy ways of using reiryoku. But to the initiated, to the clear-sighted, these are ways in which we impose our will on the fabric of reality, bringing miracles into existence. Twisting my hand slowly, I pull on the necessary strings of energy. I couldn't help but marvel at the unwinding tapestry.

That's the risk that comes with seals. Once someone finds a flaw, they can undo the entirety of your work. Feeling the final seal unravel, I knew my time was limited to implement my next steps. I needed to re-engrave the seals.

However appealing escaping sounds, the memories of Ryujin Jakka tend to humble any would-be rebel worth his salt. Without mastery of Bankai and prolific knowledge of all Kidō in Soul Society, I would never dare point my blade at that man.

Re-engraving the original seals is also not my goal. What I need is a seal that allows reishi into my cell and allows me the option to interact with things outside of the cell. However, the seal must also superficially look like the original seal and ping the commanding seals elsewhere the same way the originals did. I can only hope that the pings my new seal sends are similar enough that the Detention Unit doesn't catch the minute differences. They likely won't since they aren't the Kidō corps, but there's really nothing I can do about it if they do.

Ignoring the grime situation of being forced to flee without a good escape plan, I savour the long-lost feeling of reishi rushing into me. During my free time, I massively increased the efficiency of Project Glutton and Atlas to the limits my control of reishi allows. My stagnant reiryoku finally started to grow noticeably.

The warm feeling throughout my body from the strengthening spell was also welcome. But most importantly, I could feel Sōten ni zase take the zanpakutō equivalent of a deep breath. The scarcity of reishi in our cell had always been debilitating for him. He was essentially a wanderer in a desert, slowly withering away without his sustenance.

Gentling stoking the cold rage in my heart, I started controlling the inflow of reishi. Instead of the noticeable torrent it currently was, I smoothened it out to a gentle nondescript stream. I just needed time to grow. Time the Soul Society had forced onto me. The consequences of which I hope to etch onto the very foundations of Seireitei.