I'm Banging My Rival in a Parallel World!?

1-2) Isekai ni Tondara Rival ni Hameraretemashita!? (異世界に飛んだらライバルにハメられてました!?)
Amatatsu is a brash, but normal high school student until he wakes up in the middle of doing it with another guy!! To make matters worse, the culprit is his biggest rival, Sen! Is it really possible he's come to a parallel world where he and Sen are a coup...