I prefer a non-beta like male mc, but at this point, I'm all for her forcefully whipping out his water hose and dousing her raging ecchi fire. There is no way a straight man wouldn't have done the deed at this point. With her living with him and with a woman that is constantly trying to get tapped, with literally nothing holding him back from doing so. Especially if she is cute, ecchi and always seducing him.
He should shave his head, because clearly, his true calling is being a monk.