In the morning after a party he was in his room sighing a bit tired and frustrated, at least it didn't get out of control, right? Big mistake, now you were sleeping peacefully next to him, with bite marks and hickeys all over your neck, shoulders, and collarbone. 

Rei: Oh no...

He stays in silence for a few minutes admiring you, he felt a hint of pride although he didn't even know why, perhaps because he had already marked you, no one could touch you.