Errrm... My Heart! This is a great example of how to write a story were not saying makes sense for the characters. The reasons are well fleshed out and it's not just done for 'drama' but rather, because it's something the characters would do naturally.
The art is stunning, the story is beautiful (and heartbreaking), the characters are realistic and fleshed out, and I love everything about it. Just a stunning BL all round.
Kimi ni Ienai Koto ga Aru