Who Is Kai?

Kai Chisaki, also known by his villain name "Overhaul", is a major antagonist in the My Hero Academia franchise.

He is the leader of the Shie Hassaikai, a Yakuza organization comprised of villainous Quirk-users. Following the defeat of All For One (the overarching antagonist of the show), Chisaki believes he is destined to become the next ruler of the criminal underworld and plans to destroy the current Quirk (or superhuman/superpowered) society and return the Yakuza to its former glory.

Chisaki is shown to suffer from mysophobia, as he is under the delusion that everybody around him is sick and hates being touched since he is shown constantly scrubbing his arm, in fear of any contamination caught onto him.

Due to a combination of an old theory claiming Quirks derived from rats and his mysophobia, Kai believes that Quirks are a plague on humanity, having infected people with "syndromes" of heroism and villainy. He looks down upon those that use their abilities for either purpose, referring to acts of heroic sacrifice or petty crime as "sicknesses". Kai is highly determined to his ambition of eradicating Quirks, not only due to his phobias but also because such a thing would allow the Yakuza to reclaim the power they once held over society. Kai has no moral compass and an enormous ego, viewing himself as the only person in the world who's enlightened to the "true nature" of Quirks and deserving of the spot as ruler of the underworld after All For One's downfall.
Despite this, Overhaul's values are noted to be paradoxical, particularly his over reliance on his own Quirk, which he happened to name himself after.

As the leader of the Shie Hassaikai, Kai is usually levelheaded, thinks strategically, and can come off as nice at first. Kai possesses polite mannerisms and can be very calm and classy even to people he considers potentially troublesome. If aggravated, however, he may display a powerful and visible killing intent.

As stated before, Kai is very germaphobic and hates anything he perceives as unsanitary, frequently remarking about the unclean appearances of certain people and locations. He refuses to be touched by others or even breathe in the same air as theirs, which is one of the reasons he wears an air-filtering plague doctor mask and forces his subordinates to do the same while around him.

If blood, dirt, or some other unclean substance comes in contact with Kai's person, he will start developing hives and lose his usual composure, becoming increasingly unhinged as a result. In drastic circumstances, though, Kai will let go of his aversions to crush an enemy standing in his way, either due to pragmatism or out of sheer hatred.

Kai doesn't value humans, viewing people as pawns for their utilitarian value and being willing to experiment on them to accomplish his objectives. He carries this sentiment even towards the other members of the organization to which he has dedicated himself since childhood, treating them as expendable sacrifices for his well-being and having no qualms about killing them off for the most minor mistakes.
The masks worn by Kai's closest subordinates also remind him of this mindset; he doesn't view them as worthy of sharing the same air as his.

Even Eri, his boss's granddaughter and the centerpiece of his operations, is not spared from this brutal way of thinking as Kai frequently shames and abuses her through threats and guilt trips, seemingly to force subservience on her mind. He ruthlessly performed experiments on Eri, which involved painfully disassembling and reassembling her body with his Quirk, and had no problem with killing people in front of her, including her minders when they allowed her to escape. Kai was possessive over Eri due to her being the key component in his plans, flying into a massive rage when she was taken from him and going to extreme measures to get her back.
Despite being assigned as her foster father, Kai had no intention of parenting her and later confessed to Mirio (a 3rd year student that was involved in the raid of the Yakuza) that he never saw her as his child. Another hypocritical facet of Kai's plans was his obsession with Eri's Rewind, the ability that enabled him to fulfill his plan of destroying other people's Quirks.

In public, Kai acts as a strict yet regular father, becoming irritated when bystanders pry. He casually made excuses for Eri's bandages and fearful behavior, saying that she was simply a clumsy and badly behaved child who was afraid of being told off.

The only person Kai has ever shown genuine concern for is the former boss of the Shie Hassaikai, who rescued him from the streets at a very young age and raised him as a yakuza. Kai, to this day, still feels deeply indebted to his boss for taking him in, being adamant in returning said debt by returning the yakuza to their glory days somehow.
Ironically, despite his sociopathic mindset and inhumane treatment of others, this makes his ideals about family much more personal than any other members of the organization. Aside from this, he has also shown to value Hari Kurono, his childhood friend and right-hand man, having healed his injuries and being the only one of his subordinates he does not treat as disposable.

As a young yakuza, Kai was extraordinarily ruthless and would kill anyone who didn't show the Shie Hassaikai the proper respect, constantly getting into fights with rival gangs. Kai's boss, who was growing aware of the violent, immoral path his underling was following to uphold the name of the Shie Hassaikai, attempted to sway him towards a more honorable course, but to no avail; Kai became more and more convinced that illegal, questionable dealings were the only way the yakuza could ever restore their former honor. This immorality would lead the misanthropic Kai to develop an interest in the boss's granddaughter because he considered her rewinding abilities a golden opportunity for the Shie Hassaikai, believing that he could produce a Quirk-Destroying Drug out of her cells that would give the yakuza enough power to take control of the black market.

Despite his loyalty and indebtedness to his superior, Kai could not accept his boss's refusal over the idea, attacking and leaving him comatose to work on his plan unimpeded. Kai took over the Shie Hassaikai under the twisted belief that everything he was doing was for the sake of his boss and the organization, intending to bring his boss out of his coma after he completed his plan.

Ultimately, Kai's failure to recognize others and his obstinate nature resulted in his downfall. As noted by Tomura, even though Kai's goal was to erase Quirks and restore the yakuza to power, he hypocritically used a Quirk to achieve that plan. Despite his strong-willed attitude, he is capable of expressing genuine fear and shock, especially post-defeat, after the League of Villains took away his product and ability to use his Quirk, screaming as the reality of being unable to bring the boss out of his coma hit him.

As seen by the time of Tartarus' mass riot and breakout, Kai's imprisonment and the comatose status of his boss have left him as a shell of his former self, being rendered to a near-catatonic state and being unresponsive to everyone, anyone, and everything around him. This refractory state is seen when he had little to no reaction to the mass riot during the Tartarus prison break and later showed no response to the appearance of Tomura Shigaraki and All For One, only being able to mumble the words "Boss", in reference to his father figure. During his talk with Lady Nagant, Kai laments over having lost everything, not even wanting to exact any revenge and only cares about reuniting with his boss, mumbling about how he wants to see him again, even when close to danger.

Kai is even shown crying out of regret while begging to apologize to the boss. While he still hates Izuku (despite the latter having saved his life) and holds no remorse for his treatment of Eri, he does agree to make amends with Eri, but only so he could save his boss. This would ultimately not happen however, in order to spare Eri from reliving her past trauma.

Following the Final War, Kai finally reunites with his boss who had been awakened through advanced support items. In the face of his former boss, who admonishes him for his crimes and for causing Eri so much pain, all Kai can do is cry, snivel, and apologize, with his inhumane actions having doomed both himself and the organization that he swore to revive.

Kai's misc appearances

My Hero One's Justice 2

Kai appears in the second game as it came out in March 11, 2020 which was the year My Hero Academia season 4 was still airing. It is an arena fighting game and a really great one at that. I remember being obsessed with it and playing it a lot. Sadly though, the player base is next to non existent.

His intro and win screens are super cool and make me really happy when I see them.

In addition to his regular, human form he also has his monster form when he fused with Shin Nemoto which is named Overhaul V2.

My Hero Ultra Impact

My Hero Ultra Impact is an RPG video game which was released on February 9th, 2022. I had played it back when it was first released and I did have a bit of fun doing so but it's a gacha game so it can be a bit frustrating to play at times, especially when you don't get the character you want.
Despite that, Overhaul does have some pretty cool art from the game.

My Hero Ultra Rumble

A battle royale and a gacha game, My Hero Ultra Rumble was released on September 28, 2023. Once again, I had played it a bit when it first released but I had only played through the tutorial. I'm not really a fan of battle royale games in general and combined with the fact that it's also a gacha game I would imagine it to be at least a bit frustrating to play.

Overhaul was introduced as a playable character during Season 6, which began on July 23, 2024. I found it surprising that he was added but I ain't complaining.