There are elements of this that are great. Fumi has been in love with Shunpei since they were kids, but Shunpei has been oblivious to his feelings - until Fumi starts dating a guy at school. Shunpei has to own up to his own jealousy and makes the decision that if Fumi has to date a guy, it's going to be him. Over the course of the story, he falls in love himself, and it has a happy ending.
Now the bad parts: The early chapters demonstrate the homophobia and fetishistizing that are common in fandom and BL. For example, Shunpei's sister - a huge BL fan - is horrified when she learns her brother is dating Fumi, saying she'll be mocked at her wedding for it. She's further upset to find he plans to bottom. It's stressed that her interest in BL is purely fetish, and the attitude is pervasive in the early chapters. As the story goes along, we pick up supportive friends, but the sister - who seems to be an avatar for the mangaka and the reader - never changes her attitude, even going so far as to keep Fumi and Shunpei from being able to sleep together under threat of telling their parents.
Beyond that, this manga also wanders into dubcon territory. Several times, Fumi announces that he has no plans to stop what he's doing, even if Shunpei says no. And there are times he says no, and Fumi doesn't listen. That's common for this genre, not specific to this manga, but it perpetuates the idea that noncon can be sexy if everyone gets off. Not so, and kudos to Shunpei for kicking Fumi off the bed toward the end of the story when he didn't stop when Shunpei asked.
Overall, a really sweet story, but I felt like the mangaka herself is the one who has a lot of these beliefs, and that made reading this less than pleasurable at times.
Elektel Delusion