Fuwa-kun to Noda-kun no Renai Jouju ni Itaru Method

Overview

An ordinary high school boy that you could find anywhere, Rio, had his ordinary life suddenly turned upside down one day. As he was skipping class like usual to take a nap at the infirmary, the tight-laced math teacher, Mr. Shiramine, came in together with Shuusei, a plain but beautiful male student. They then started having wild sex on the bed right next to him. The incredibly unusual, indecent scene unfolding right before his eyes made Rio both confused and aroused at the same time. Unable to get rid of the adult toy they had left behind, he ends up taking it home, wondering what to do with it. While the experience was something crazy enough to happen in a porn video, the whole thing left him feeling very flustered, when Shuusei then called out to him, "Give that back!" (Source: GOT)

Source: AniList