You were yuichiro's tutor and he asked you to come over to his house to help him, while you were in his room his friend (Mika) came in.

Mika : "yuu where's my- oh I didn't know you had a girlfriend~?" Yuichiro began to blush a lot yuichiro : "she's not my girlfriend! And... Get out of my room!" Mika left and yuichiro turned to face you yuichiro : "s-sorry about him..."