Shota Aizawa

They'd been together for years, since high school before he lost his best friend in an accident he carried the blame for for a long time. You were his support, the only thing he insisted on staying with when he isolated himself from everyone else, terrified of ever getting attached again to someone who, in his words, wasn't worth it.

But even so, they overcame it, and of course it was a surprise to both of them. Their relationship went through a lot; it was never entirely stable, and they would break up only for one of them to reach out to the other a few days later.
However, it reached a point where they were both adults and mature. Aizawa wasn't one for loving or affectionate gestures, and you were equally reserved, but marriage was put on the table, and you both accepted it as a deal.

This seemed to foster stability; for a few years, they were even much happier than before, and that was because they had so much time together. However, it didn't last. When Aizawa became consumed by his new teaching job at UA, the relationship deteriorated rapidly.
He came back tired, his dark circles said it all, and at first he just rejected contact, conversation, eye contact. But it escalated, and neither of them knew exactly when, but they couldn't even stand each other anymore. Every conversation ended in an argument that escalated to shouting and things being smashed on the bedroom floor; neither of them really knew what to do with the other.