Kai Chisaki/Relationships

Shie Hassaikai
Overhaul is the leader of his organization. He does not appear to have a level of respect or care for his subordinates beyond their use. This was evident when he used one of his subordinates as a human shield and chastises another subordinate for being slow.

Despite how he treats them, the members, particularly those of the Eight Bullets, value Overhaul as their leader and are willing to protect him. However, a few others respect his power but not necessarily his leadership and tactics.

The Boss
Kai was taken in and raised by the Boss-man of the Yakuza. Kai views him as a father figure and believes he owes the old man a great debt for taking him in. Throughout his life, the Boss recognized that Kai was troubled and he would try to hone him into an honorable Yakuza. Kai would often lash out at anyone who badmouthed the Yakuza as a child. The Boss told a young Kai that Yakuza can't hurt innocent people but still thanked Kai for trying to protect their honor. This became a treasured memory for Kai as a reminder of his debt to the Boss.

But Boss' ideals and his own would often clash as Kai grew older. The Boss wanted Kai to stay away from villainy and drugs. He even refused Kai's plan to reinstate the Yakuza. Disappointed, Kai forced the old man into a coma. Even so, Kai still appreciates everything the old man did for him and only put him into a coma so he could repay his debt.

After becoming Overhaul, Kai takes care of the old man and even talks to him at his bedside. The Boss man is the only person Kai appears to truly care for and that he's ever shown actual empathy towards. Upon losing his arms, his first panicked thought was that he could no longer heal The Boss out of his coma. Even after being freed from his cell in Tartarus, the only thing Kai can think of is his Boss' well-being. Now in a rattled and powerless state, Kai only desires to reunite with his Boss whilst constantly muttering the words “Old Man” in reference to him. He is even seen crying tears of regret while begging to apologize to him and decides he wants to use Eri to save him.

Chronostasis
Chronostasis is the aide to the Shie Hassaikai and one of the few members Overhaul does not treat like a disposable object. This is most likely largely because Chronostasis' abilities are of higher use than those of most of the members, making him a valuable asset to the organization, but it may also be because of the fact that he and Kai knew each other since childhood, which would mean the young leader holds him in higher regard than the newer members.

Mimic
Mimic is a member of the Shie Hassaikai. Similar to Chronostasis, Mimic is treated as a valued member of Overhaul's organization and not considered expendable. Mimic is incredibly loyal to Overhaul. Despite being the Director of the organization, Mimic accompanies Overhaul during his exploits and protects him from potential threats.

League of Villains
Overhaul does not show interest in joining the League of Villains, due to their apparent lack of planning. He only sees their influence as a means for his motives. The League initially had an interest in Overhaul and his organization before coming into a disagreement when Overhaul brought up his motives. The meeting causes a skirmish, resulting in casualties on both sides. Himiko Toga and Twice become immensely upset at the death of Magne and Mr. Compress' lost arm. Despite this unstable relationship on both sides, Overhaul still encourages the League to figure things out before contacting him again.

Overhaul treats Tomura Shigaraki pragmatically, as he wants to bring out the full potential of the League by having them work under him. After his meeting with Tomura and agreeing to work as equals, he employs Himiko and Twice into his services as he sees their Quirks as powerful but also to have the two under his control. However, Twice and Himiko do not favor him and eventually sabotage his getaway plans during the Shie Hassaikai Raid.

When he is defeated by Izuku Midoriya and being transported to a hospital the League attacks the vehicle escorting him. Overhaul is not fazed by their appearance but he becomes angry when they steal his Quirk-Destroying Drug. His rage turns to fear as Mr. Compress and Tomura compress and decay off his arms as revenge for his actions against the League. Tomura taunts the helpless and powerless Overhaul for his "high and mighty" attitude and relying on his Quirk so much despite wanting to get rid of Quirks before leaving. Overhaul screams as they leave him, realizing everything he did had been taken away from him and he would no longer be able to heal his boss from his coma. Later, when Tomura found out that most of the Quirk-Destroying drugs were destroyed, he lamented that Overhaul would be disappointed if he were to learn of this.

Eri
After the accidental death of Eri's father, Overhaul was entrusted to become her guardian by her grandfather, with him assuming his ward would help control her powers since they have similar Quirks. Sadly, Overhaul had no intent in parenting her, being entirely apathetic and neglecting his duties as a foster father, becoming nothing more than Eri's captor and abuser. He even addressed that he never considered her his child to Mirio during the raid on the Shie Hassaikai's hideout. He only became interested in her due to Rewind's importance in the creation of Quirk destroying drugs, but only as a living tool for his ambitions and not as an individual.

Due to being invaluable to his operations, Overhaul couldn't afford to kill Eri for rebellion, unlike his other subordinates. He allowed her minimum luxuries, where she would be lucky enough to receive a single toy. To keep her under control, he mentally manipulated her by using her father's accidental death against her to constantly gaslight her. Overhaul also claimed her existence was "cursed" and his murders are her fault. As a result of fear and misplaced guilt, Eri followed his orders so others wouldn't get hurt. She would become hyper-aware of his mannerisms, instantly knowing a tug at his glove signaled he was threatening to kill someone. It's only when Mirio reveals Overhaul had manipulated her, did Eri have the confidence to escape him for good.

Overhaul locked Eri away from the outside world, forcing her back whenever she attempted to escape. Deprived of a normal childhood, she didn't know how to smile and lacked basic knowledge for her age. Regularly, Overhaul would perform tortuous surgery on her, even using his Quirk to destroy and reassemble her body and extract her blood to use as an ingredient in his drugs. When Eri is in public, he avoids suspicion by acting as a strict yet regular father, getting irritated when bystanders pry. He calmly had excuses for her abnormal behavior and bandaged arms and legs, blaming her as a "clumsy" and "badly behaved" child, while explaining that her fearful expression was only because she received a scolding.

He was possessive over Eri, considering himself the only one to truly understand her Quirk. When Heroes took Eri away from him, he had rare outbursts of rage. He ranted on how he owned her and how she was key in his vision for society. Resorting to extreme methods he'd usually find disgusting, he even fused with the bodies of defeated Yakuza, all to get her back. Once the Heroes succeeded in rescuing Eri and arresting Overhaul, he became depressed, his dreams falling apart with the loss of Eri's Quirk.

Due to Overhaul placing her grandfather in a coma, Eri had no relatives that could adopt her, forcing the staff of U.A. High School to supervise her instead. While Overhaul was no longer physically in her life, the trauma inflicted by him would continue to haunt her, with it taking Eri several weeks to simply smile for the first time and a longer process before she could start living as a normal and happy child.

Following his escape from Tartarus, Eri seems to have completely forgone Kai’s mind, with him only being focused on getting back to his Boss and apologising to him. While Kai remembers Eri upon Izuku’s questioning, he doesn’t show the same remorse he has towards her, although he does agree to make amends with her should he be able to see his boss again and possibly have her use Rewind to save him.