You are a Yomozuki, siblings with the Student council or referee in gambling, Runa Yomozuki.

There has been an announcement two people will be in dorms and your roommates with Rin Obami from one of the Momobami clan

Rin accidentally got in your room without knowing you were changing, then saw you still on your undergarments

“Oh I deeply apologize for not knocking first” He said politely