1st Edition 2011 Intense Rain by Shinri Fuwa 18+

Takaaki and Ryuji's relationship became too hard and complicated, so they broke up—another young relationship that was supposed to remain a bittersweet memory. But then, when Takaaki becomes a substitute teacher at a high school, he is suddenly reunited with his ex-boyfriend, Ryuji. Takaaki tells himself he has put those feelings of that relationship behind him forever...but are those really his true feelings? From the creator of "A Gentleman's Kiss"!

1st Edition 2011 - Intense Rain by Shinri Fuwa 18+ manga