He bit back a grunt of agitation as the guards hefted him from the gurney and into his chair. He didn't react as each of his arms and legs were bound tightly to the chair, though he did shoot one of the men a tight-lipped smile as he tugged a little too enthusiastically at the restraints. With their work done, the men left from the room without further comment.

He briefly tested the strength of the restraints, and was unsurprised to find that his arms didn't so much as twitch. Unsurprising, Tartarus was notorious for good reason and the men and women responsible for the safe-keeping of the prison took their jobs seriously. They'd even done their research, no doubt working with that upstart brat to make sure there was nothing he could use to mount an escape. His prison cell was less of a cell and more of a padded room. Four bleached, padded walls and the single chair he was strapped to were all the dignities afforded to him in his new home.

He stifled a grunt of agitation as his neck itched under the quirk-dampening collar. It wasn't the lone tool the fine men and women of Japan's law enforcement had attached to him to keep him secured. The collar around his neck was matched by similar collars and restraints around his wrists, ankles. During his processing, they had inserted a security chip into the small of his back, meant to diminish his physical quirks. Even the IV drip was filled with a special chemical meant to keep him sedated, and unable to think or concentrate clearly.

But in spite of all of the precautions, the poor fools vastly underestimated the scope of his abilities. They couldn't possibly begin to comprehend the full scope of his capabilities, and his most powerful and most terrifying quirks were not the type to be seen in a climactic battle with an overly strong man-child. More importantly, they were not the type to be considered useful in planning his escape and his return.

But he would could focus on that later.

He had more pressing matters. Namely, his broken and failing body. Even now, he could feel his life draining away even quicker than before. The battle with his adversary had accelerated the damage that had already been done. He had three maybe four months at most, and now his plan for a new body was gone.

He made a mental note to deal with that little problem later.

First things first, he needed to find a replacement for Shigaraki. Not an easy task if he were being honest. Shigaraki, for all his petulant anger, had been his ideal candidate. Young, powerful, and deliciously malleable. The bile of frustration threatened to wash over him, but he squashed it. It mattered not. He'd long since cultivated the ability to have a short-term memory when the need arose.

And now was such a time.

Reaching down into himself, he pulled out on one of his most unique quirks, and began to utilize it. This particular ability was one he treasured rather dearly. He'd taken it from rather tragic young man in the Philippines over a century ago, and it allowed him to "feel" all of people around him at any given time. It was an overwhelming sensation, as the quirk not just felt their presence, but felt their every feeling. Every fleeting emotion.

It was no wonder that poor Nathaniel had wanted it gone. The tragic man couldn't control the gift, and it had driven the man mad.

But another man's loss and all that.

And so, he began his search. He had a particular set of attributes in mind. A particular mindset. They needed to be strong of will and of mind, but also malleable. A seemingly contradictory amalgamation of emotions but humans could be complicated creatures, and he was certain he would be able to find someone. And after two weeks of searching, he found what he was searching for. A delightfully complicated man, with a tantalizingly fascinating quirk. He was driven, that much was very clear, if the strong sense of determination and persistence wafting off of the man was any indication.

There was deep resentment, anger, and hatred for society at large brimming under the surface. But for all of his single-minded focus and determination, the poor man was also beautifully susceptible to some minor manipulations. His own phobias and fears for the unknown and the unclean drove the man to near mania.

He was an ideal candidate, and with his time drawing near, he didn't feel that there was time to look for any alternatives.

Kai Chisaki would have to do.

With his decision to move forward made, he began the second phase of the operation. This meant utilizing a quirk he acquired from an old French woman, it was nothing exceptional, at least not when Elyna had the ability at least. It was a mundane telepathic ability, allowing the user to infiltrate the mind of another. There was nothing that could be done once inside the mind of another, but that didn't matter, it was all about opening the door. And once that door was open, it was time for another ability of his, this one allowing him to project his own psyche onto that of another. It wouldn't allow him to take over the body outright, there would be a time and place for that, but it would allow him to begin pushing young Chisaki in the right direction.

But one step at a time.

So he settled in to watch Chisaki. Silently feeling and observing him. Poking and prodding around in the man's psyche. Getting a feel for the man, and putting together a strategy for positioning him into the right place to be susceptible. In his observations, he made another mental note to inquire more deeply into this little girl the man seemed to be holding captive.

His first intrusion into the man's mind was subtle at first. The man was too intelligent to fall for anything to overt. So he started with minor whispers. Small thoughts, thoughts that were so un-intrusive, the man would pass them off as his own and forget about it minutes later. But that was completely acceptable, he just wanted the man to become accustomed to the sensation.

For weeks, this trend continued. Little nudges, minor influences. Every time the man made a decision, an intrusive thought would pop into Chisaki's mind, guiding him in the direction he already favored. It was a straight forward plan. Manipulate the man by steadily creating a positive association between Chisaki, and the voice in his ear. The voice that always told Chisaki what he wanted to hear. As the weeks bled by, the voice became louder. More insistent, and Chisaki continued to follow it. After all, the voice had not led him astray thus far.

But then…a curiosity. Chisaki encountered someone…unexpected. A mass raid on his little hideaway resulted in a confrontation between him and a familiar youth with an even more familiar power.

Curious.

It would appear that his adversary had finally chosen the ninth wielder. A wielder with a rather impressive talent for one so young. It had been a short, one-sided confrontation. Even with his seemingly impressive quirk, Chisaki was so simply no match for the wielder of One for All.

But that was of no matter. In fact, this was a beautiful thing. He fought back a smile. How delightfully convenient. That the wielder of his foolish brother's power, would be the ultimate downfall of the society he had fought so violently to protect. It was a day after the confrontation with the Ninth Wielder that Chisaki arrived in Tartarus that the final steps were out into motion. Had he been more of a religious man, he would have called it divine providence. But as it stood, he was happy to call it lucky happenstance.

Chisaki's body might have survived the fight with the Ninth Wielder, but his mind certainly had not. The poor man's psyche had been utterly fractured by his confrontation. Unable to comprehend his own failure to live up to his own goals and promises, he retreated into himself. A shell of a man barely clinging to the edge of sanity. A sanity that only grew frailer and frailer as the whispers in his mind grew louder.

It was perfection.

Chisaki's fractured psyche provided precisely the vulnerability needed to begin the second phase of the plan. The small voice, once little more than a whisper, became a reverberating shout. His voice became Chisaki's sole friend in the world. Sole confidant.

And Chisaki welcomed him in with open arms.

He would have laughed, were his ribs capable of withstanding it. The poor man was becoming even more deluded than young Shigaraki had been. As the weeks continued to stretch on, the voices began to change. No longer did they provide safety and comfort; offer reassurances and confirmations that Chisaki was on the right path. Instead, they began to offer him a deal. A deal to harness even grander power. A power unrivaled in the world. The kind of power that would allow him to rebuild his beloved family, and cleanse the world of all those he deemed unclean.

Chisaki leapt at the opportunity. All but begging for the voices to do whatever was necessary to grant Chisaki the power to cleanse the world of the impure.

It was all the incentive that was needed.

One month to the day, after Kai Chisaki was brought to Tartarus, every klaxon in the facility began to scream. Medical professionals and guards swarmed the halls, descending on the maximum security cell of the terror of All for One, whose vitals had suddenly, and violently dropped to nothing. But in spite of the best efforts of the medical professions on the scene, there was nothing that could have been done to save the failing body.

At a little after one in the morning, the body of All for One died. Over noise of the alarms, and the chattering of the inmates, nobody heard the laughter coming from Kai Chisaki's cell.

Where two lives had ended, a new one had begun.