Need help finding this yaoi from my memory!

All I remember is it’s about a high school guy who gets visited by a sx demon who makes it a mission to get this guy to have sx and so he puts him in these situations at school.

For example, the one I remember vividly is: He strips the guy, ties him, writes something like “insert here” on his belly and then puts him to sit on a school toilet. So when another student goes to use the restroom, he’s like “Oh, [the main guy’s name], I didn’t know you were like this. Well, okay then” and proceeds to do what’s written on his stomach, but then another guy comes in and they both do it at the same time.

This is all I remember, and I remember being like what am I reading, but it was really hot so I wanna reread it 😅

Oh, and it was only a few chapters long!