A man is reunited with the guy he'd been in love with in high school, and they fall into a physical relationship that grows serious, but they have to navigate jealousy and family issues. There's a movie version that I don't care for, but I really enjoyed this manga. I've read it three times - and the third time was probably my favorite.
Kurata is a jackass when we first meet him. He's never understood the feelings he has for Keisuke, going back to high school, and sleeps with him to confirm that Keisuke had once liked him. He continues to use him for sex - often forcing it - but eventually falls in love and experiences a pretty significant personality change. He's sweet by the end, and Keisuke calls him out on his terrible behavior and breaks up with him for a while - I liked that. Includes lots of cute oneshots about their life after moving in together.
Junjou