Responses
http://www.mangago.me/read-manga/intertwining_lives
I love this manga
http://www.mangago.me/read-manga/hachimitsu_to_clover/
A very beautiful story in general, plus it has what you're looking for (and much more).
Anyone knows any manga about unrequited loves that remain unrequited? Yaoi or not, it's fine. I'm in the mood for a heartbreak ;_;