Kosei Tsuburaba/Relationships

Neito Monoma
Kosei and Neito appear to have a friendly relationship. During the U.A. Sports Festival Kosei went along with Neito's plan to throw the qualifier. He also joined Neito's team for the Cavalry Battle, during which, he was the only teammate to voice his opinion on Neito's actions.

Tsuyu Asui
When Kosei got restrained by Tsuyu's tongue and dragged off to Team 1-A's prison, it appears that he presumably developed a small crush on her. While getting captured, he seemed to be mostly thinking about how Tsuyu's tongue was wrapped around him.