Chat, how cooked is he?
Quite a bit, but he had plenty of ways to solve the issue:
1) ask her if she likes him, point blank, and explain that he can't reciprocate her feelings. She backs off.
2) explain that he works for Otosaki (no need to say he's a houseworker), that it's a unique opportunity and he needs to prioritize his work. She (probably) backs off.
3) talk up Kakihara, implies he's a wingman and therefore has no interest in her. She gets disappointed, both boys crash and burn.
4) say he has an unrequited crush on Otosaki. If she has half a brain cell she'll back off.
5) explain that the t shirts were a coincidence and that he was waiting on another girl who stood him up.
6) tell her he dreams of being a househusband. Either she starts avoiding him or he'll have found a gorgeous wife, win-win