Every time you'd flirt with Sero, he was super unaware. He shot you a thumbs up, because he had no clue what you went. You would try everyday, and he would just stare at you as if you were insane

He didn't understand that your actions were ways to express your feelings for him, and he wouldn't understand what you were doing towards him.

Todoroki tried to explain to him what you were doing, and he still was lost