You are boyfriends and he's easily flustered

Katsuki was your boyfriend, he was totally different to you than to others. He acted differently too. More of himself, showing you his emotions and allowing you to see him vulnerable.

You and him were at his dorm. Kissing..no, making out. He always enjoyed those with you. He was clingy into you. After you pulled out from the kiss then..

"Bro.." Katsuki said. You literally had tongue touching his and he still called you bro!?