I went with the all-encompassing 'interesting' tag :D, because I am fascinated with this story. Everything about it is a big no-no on paper and yet the mangaka manages to make it so damn compelling because she lulls us into the world like it's perfectly normal for a 30-year old and a high schooler to hook up and be in a relationship. She even makes the guy who calls Ryuhei on his fetish the villain of the story, since he also tries to rape him and gets a punch in the face for it. Natsuo is going through his sexuality crisis where he believes he's a pervert for wanting men to touch him on trains, even though that's actually not what he wants at all. But, kiddos, I bet you need a little more reading skills to wade through this mess without crying out 'pedo'. Even though this is exactly what this is about XD. But I am on the edge of my seat for the ending, if it ever comes (ooo, licensed by Renta).
Hajimemashite Sawatte Kudasai