You're always like that...

You treasure the people around you so much that your own well-being takes a back seat...

That's your very own brand of kindness, but it's also a kind of self-satisfaction.

I think I've got another reason to start crying...

Let's be happy together, Rintarou.

This do you solemnly vow, till death do you part? Lit. "Do you swear?" He's supposed to go "I do" at this point, but "Do you swear" is a bit too far from the standard procedure in English.