Y'know, if he knew that the reason why Ruka likes him is because of her heart condition. I think he should stay with her if she doesn't like Ruka. If she's always with him, she will no longer feel as excited every time she's near him.
I'd probably kill myself if I was on his shoes.
But now that I think about it, leaving my daughter will be too sad so I think that I won't be able to leave her alone.