Hitoshi and Katsuki had met during their internship. At first, they hated each other, but eventually their rivalry and teasing turned into affection.  They loved each other. Most people said that relationships that happened during it internship or residency never lasted, but there’s seemed to last anyways. But then it was their last year of residency before the boards. There was this one attending that had arrived earlier that year, and he was a well-known and well respected surgeon, he was perfect by most standards but despite that for some reason, Hitoshi had always had a bad feeling about him. And one day a little girl and her twin brother came into the ER by themselves, and the boy was bleeding and barely conscious, and the little girl didn’t look as bad, but she had bruises all over her. Anyone who looked at the situation would immediately have suspicion of abuse but first things first was to make sure they were OK and treated. Hitoshi ended up helping treat the little boy and the attending was the same one that Hitoshi had always had a bad feeling about and everything seemed fine until later after the boy was stable and him and his sister were put in a hospital room on the pediatric floor, and the father arrived. The father looked frantic like any parent would if they had no clue where their children had been for a considerable amount of time but there was something else about his panic. Something that felt painfully familiar for Hitoshi. When Hitoshi was younger, his biological parents had abused him for a long time before finally just abandoning him. Everything seemed even more clear when you were in the hospital room and the dad was there. There were signs that were almost impossible to Miss as a medical professional, the way the children flinched whenever he came near, the way the father’s jaw tightened every time, and then when the father had left for a moment to go to the bathroom or something and Hitoshi and the attending, we’re both in there, and the little boy had admitted that his father was abusing them and the attending brushed it off and told the little boy not to say things like that about his father and that discipline was normal. And then, when the father came back into the room, the attending told him that the little boy had said that. Later, the two children were discharged with their father and Hitoshi never got a chance to actually help them. He tried for weeks afterwards to get someone to do something. He told Katsuki and Katsuki tried to say that maybe it was a misunderstanding or something because he wasn’t in the room when it happened. Hitoshi told Katsuki that he was going to confront the attending and Katsuki obviously tried to talk him out of it because they were so close to their boards and that attending could ruin their careers and he wanted Hitoshi to be smart about it, but Hitoshi said he couldn’t just standby after what happened. So Hitoshi ended up confronting the attending and the attending admitted to it and said that abuse is just a word people made because they didn’t like discipline and he told Hitoshi that it was his word against his own. The attending ended up filing a complaint about Hitoshi saying that he was making untruthful claims against him, and that Hitoshi should be kicked out of the program, and Hitoshi just snapped and kind of destroyed a scrub room. Hitoshi was kicked out of the program and blacklisted from all the hospitals in the city and most of the neighboring ones. Hitoshi and Katsuki ended up getting into an argument about it because Katsuki had warned him and told Hitoshi that he should’ve just let it be and they ended up breaking up and Hitoshi moved a couple cities away in order to join a new program and finish his residency and fellowship and now he is a full-blown surgeon and him and Katsuki haven’t talked since Hitoshi moved. And Hitoshi has made a name for himself as a respected neurosurgeon, and he gets an offer from the old hospital he used to work at when he was in his residency with Katsuki and because the hospital is very state of the art and just a really good hospital, and the old attending is gone, Hitoshi decides to take the offer and he just kind of assumes that there’s no way Katsuki is still there as an attending and then he gets there and it turns out that Katsuki Bakugo is the chief of surgery. but the first time they see each other after a decade of not talking is at a bar the day before Hitoshi is supposed to start the job and they’re both considerably drunk to the point where considering they hadn’t seen each other in a decade, they did not recognize each other and Katsuki ended up inviting Hitoshi to his house to drink some better alcohol and then they ended up having a fun night and in the morning Hitoshi left before Katsuki woke up and he never actually got a good look at Katsuki so he had no clue that it was Katsuki until he got to work later and everything clicked.