I'm so beyond impressed that they didn't ended up together, yes yes yes! I think is one of the few yaoi's where they don't necessarily have to be together, god bless this author.
If anyone disagree let's all remember everything:
1. The mc was figuring out his sexuality and identity and was very conflicted, about it, he as far as we know may be transexual, anyway he has so much to live,and he can have other loves, because he has a platonic love with Masaki wich is fine.
2. Masaki is straight and even if he is not prejudiced about homosexuality that doesn't make him pansexual or something else, he is very problematic and has a lot of issues, besides he just ended up a relationship, so if the relationship with the girl he loves didn't work (for any reasons) is stupid to assume that they can get together and be fine.
3. I really enjoyed the drama and all the characters are very special in their own ways, specialty the mc with his past, and how he grow as a person, and learn to accept himself for who he is, whatever he is.
4. So at the end they weren't meant to be and is fine, both are very different and they need someone that can understand them and accept them, like they both have their own hands full of issues for them to have a nice and sane relationship.