Rei is Enji's wife. Endeavor bought her family over to marry her through a Quirk marriage. It's revealed he chose her because of how her Ice Quirk counters the drawbacks of his Hellflame Quirk. The fact he remembered her favorite flowers even though she mentioned it once during the first time they met seems to show he really cared about her at the beginning.
However, the relationship between them began to get worse when Enji's obsession to overcome Toshinori Yagi led him to train the children he considered capable while neglecting those who weren't. First, he started with Toya, whom he rejected for inheriting his mother's weak constitution. When he started training Shoto when he was still very young, his wife tried to stop him, but Enji refused to listen and told her to stay out of his way, smacking her around when she interfered with the training of Shoto.
Enji's constant abuse on her and their children, led Rei to a emotional breakdown and she ends up hurting Shoto. After this incident, Enji ends up having her put away in an institution. It's implied the worst of it started after what happened to his oldest child Toya.
Although it may seem that Enji does not love his wife, he actually has been visiting his wife at the hospital often, though he hasn't seen her face to face. He left her a flower that she once told him she liked. After realize the damage he has done to his family due to his behavior, Enji tries by all means to fix the situation with his family, accepting the possibility that they can never forgive him.
Finally, he concludes that in order for Rei and their children to be happy, he plans to have Fuyumi, Natsuo and Shoto move in with their mom in a new house built in a more convenient location and has more or less cut himself out of their lives.
Originally, his oldest son Toya was supposed to be his successor because his fire Quirk gave him flames more powerfull than even Endeavor's. As such, Endeavor tried to train him and teaching him one of his secret techniques. Unfortunately, Toya inherited his mother's weaker constitution preventing him from improving it. It is implied that, at some point, Endeavor's hard workouts caused Toya's death.
Apparently, Enji showed no guilt about this accident, but recently it has been shown that he also acknowledges that he feels it's his own fault for Toya's fate. The death of his eldest son was something Enji could never forgive himself for. Enji usually prays at Toya’s Butsudan Buddist altar in his home, and wishes he was here.
As with her brothers Toya and Natsuo, Endeavor neglected her and didn't want to use her as his successor. Despite this, Fuyumi is the only child who is more able to look past their father's faults and forgive him for his previous behavior, especially since her father was trying to atone for his mistakes and be a better person. Fuyumi is more than aware of how messed up her family turned out because of Endeavor's abuse, while expressing some fear of it, but she is the one who supports Enji the most in his effort to improve and fix his family issues.
Fuyumi goes out of his way to help her father to mend his relationship with her brothers, and in this way they can be a normal family. Although her initiatives have not yet been very successful, Enji thanks his daughter for all the support she has given him, thinking that Fuyumi doesn't know how much he has been saved by her.
When he leaves with the boys, he once more thanks Fuyumi who only responds to his gratitude with a smile. Endeavor later revealed that he is building a new house for their children and their mother, while he remains at their house alone.
As with his sister, for years Enji neglected his second son Natsuo due to not inheriting a powerful Quirk to surpass All Might. Enji deemed him a failure and did not put much thought into his upbringing, This is why at some point Natsuo even mentions that he hardly remembers his father.
After regretting his previous behavior towards his family, Enji is more than willing to do everything possible to amend his mistakes towards them, although he is perfectly aware that his son detests him, and he knows that his hatred towards him is more than justified. Enji tells Natsuo he will change his ways, but Natsuo cannot accept this sudden change and has no problem with letting out everything he thinks of Enji to him, which includes his full anger about the fact that Fuyumi and himself were neglected, the abuse he put his mother and Shoto through, and being the main cause for Toya’s demise.
He still feels the need to try and reconnect with them as he has his daughter arrange a dinner for Shoto and his friends. During the dinner, he and Natsuo are still on tense terms, despite Fuyumi’s attempts to mend it. Natsuo decides to leave earlier so as not to be in the same room as his father. Shortly after leaving dinner, Natsuo is captured by Ending, a criminal who wants Endeavor to kill him. By putting his child in danger, Endeavor freezes because he's traumatized by the look on Natsuo's face. Fortunately, Shoto, Izuku and Katsuki manage to defeat Ending and rescue Natsuo.
Endeavor embraces Natsuo, grateful that his son's life is safe. As Natsuo breaks free of Endeavor's grasp, Endeavor confesses that he is regretful for what he did to the family due his negligence and the damage caused accordingly. Natsuo tells his father he doesn't care and declares that, unlike his mother, Shoto, and Fuyumi, he is unable to forgive him. Endeavor responds that he sees Natsuo as kind enough and states that it's okay if Natsuo doesn’t forgive him because he's not looking for it, he just wants to atone for his mistakes.
Crying, Natsuo questions why he has to be the only one to try and proactively change and what exactly will Endeavor do to atone. Later, Enji confesses he will have a new house for him, Fuyumi and their mother, as he realizes that the only thing he can do to help his family is to take himself out of the equation.
Enji is Shoto's father. Their relationship initially starts out poor: Shoto grew up experiencing his father's abuse not only towards him but also his mother. As explained during the Sports Festival, Enji regards Shoto merely as a tool to surpass All Might, seemingly because Shoto possesses a perfect mix of both his parents' quirks, something his other children do not. As a result, Enji put Shoto through ruthless "training" which caused Shoto a severe degree of physical and emotional pain. Shoto, harboring a bitter hatred towards his father on account of this as well as the abuse towards his mother, refuses to use his fire powers in battle until Izuku Midoriya reminded him of his mother's encouragement.
After Shoto used his fire power in battle, Enji was visibly excited, although Shoto still made clear to him that they were not on good terms. Nevertheless, Shoto accepted his father's field training offer, showing that he realizes his father's success as a Hero.
Enji later expressed pride in his son after he succeeded in his Hero license exam - he called him his son not his tool as he had previously done. Enji tried to pat his son on the head, though Shoto gave him the cold shoulder. Undeterred by this rejection, Enji simply told his son he would try to be a better hero and man that Shoto could be proud of. Shoto simply shrugged him off but smiled to himself in response.
Enji and Shoto met again after his battle with High-End, Shoto brought up Enji's scar and spoke rather tensely to him. Once Natsuo confronted Enji and left, Shoto spoke up and called him a great hero after his success. Enji was surprised and listened as Shoto voiced while he hasn't forgiven him yet, he sees the changes he is making while looking forward to seeing what man he would become.
A sign of Enji trying to improve his relationship with Shoto is when he tries to contact him on his phone to teach him a new move while reflecting on how he treated him in the past and how he wants to support his son on the path he has chosen.
Fuyumi organized a family dinner to which she invited Izuku and Katsuki as well. Unfortunately, dinner does not end too well due to family drama. Despite this, Izuku tells Shoto that he feels he's getting ready to forgive Endeavor, as he feels that if Shoto truly hated him, it would be fine to not forgive him, but Izuku voices his thoughts on that Shoto is a very kind person waiting for the right moment.
Ten years before the start of the series, Toshinori once had a talk with Endeavor and since then, they have not spoken to each other. It appears that Endeavor has an intense rivalry with Toshinori (one sided on Endeavor's side as Toshinori tries to be friendly with him). This rivalry with Toshinori is so great that Endeavor decided to have a child that would be able to surpass All Might. Endeavor despises Toshinori's "easy breezy little attitude", finding it to be annoying. Despite his antagonism to All Might, Endeavor does have a begrudging sense of respect for his skills and strength.
However, upon learning and seeing his true form, Endeavor was furious that his rival's true form was so meek and small. His disdain of All Might only intensified after the latter retired as a Pro Hero and Endeavor would be given the No. 1 spot, which he always wanted but furiously refuses it, due to the fact he did not earn it nor does he feel he deserves it.
Despite this he is not incapable of showing All Might respect, as he thanked All Might for bringing his son back to him. He sincerely asked him later how he was such a capable Symbol of Peace.
During the Provisional Licensing remedial training that Shoto attended, Endeavor chastised himself for not attempting to be a kinder hero like All Might, but accepted that that is simply not who he is.
Enji did not like the young heroes' attitude and was especially annoyed when the latter made comments on him. However, he kept his composure and agreed with some of them. Later, he confronted Hawks on his snarky attitude and the latter explains that he tried to help Endeavor on the podium as he sees that Endeavor is fit to be a new leader to support everyone after All Might's retirement. Enji almost left dissatisfied, though Hawks requested a team-up as he needed his help in investigating concerning sightings of Nomus.
Endeavor first meets Izuku during the U.A. Sports Festival before his fight with Shoto. He commented how his power was similar to All Might's and that it's Shoto's duty to surpass All Might, so Izuku shouldn't fight pitifully in front of him. Thinking back to what Shoto told him about his past, Izuku tells Endeavor that he isn't All Might and that Shoto isn't him either, annoying the Pro Hero.
The two meet again when Endeavor accepts him and Katsuki as interns for the Hero Work Studies under Shoto's suggestion. Izuku notes that the atmosphere he had back then was different from the one he had now. Endeavor, in turn, recalls what Izuku told him back at the festival on how Shoto wasn't him.
Endeavor initially didn't want to train him and Katsuki, but after receiving Hawks's coded message, he decides to train them. After he hears about the complications of Izuku's Quirk and it's new power, he tells him how the both of them are burdened with difficult Quirks, leaving him confused.
Endeavor thanks Izuku and his other two Interns for saving the life of his son Natsuo.
Endeavor met Bakugo when he and Midoriya were invited by Shoto to be trained by his father. This is something he did not like because he would have preferred Shoto to come alone, and didn’t hesitate to let them know. As a result, Katsuki has no problem bluntly telling Endeavor that he is a jerk, although he says he will put up with it if that means he can see how the top hero operates. Katsuki's attitude displeases Endeavor and he asks Shoto if he really is his friend.
Despite his initial refusal, Endeavor also decides to train Katsuki and Izuku in addition to his son. During training, he does not hesitate to recognize that Katsuki has potential, although he does not accept excuses from him for being too slow, so he gives him some advice to improve his skills.
League of Villains
Enji met him after defeating High-End and was confused by the latter's familiarity with him. Enji soon recognized him as Snatch's killer and was disgusted by his callous disregard for the hero. The villain would try to attack but would retreat after more heroes appeared though told Endeavor they would meet again while calling him by his true name.
Enji meets Hiroshi Tameda while walking with Hawks in Kyushu after the JP Hero Billboard Chart announcements where he notices him and his friends telling him to get an autograph. Enji approaches Hiroshi and offers his hand to shake, only to be taken aback when Hiroshi freaks out by his new behavior and listening to the fan say that Endeavor is cool when he doesn't try to indulge in fanservice, leaving the hero questioning his style of approach.
After Endeavor's fight with Hood, Enji returned home to his children. After listening to Natsuo's rant about his out-of-the-blue change and him leaving the room, he sees on the news what Hiroshi said to the press to keep supporting Endeavor's fight. This causes Enji to realize how much Hiroshi's support meant to him, and what inspires him to secure a future for the next generation.