Help looking for bl manga

Umm I remember : All boys school setting, MC is a fudanshi who likes to ship his classmates, taking pictures of them sharing a drink, riding bicycle together,etc.
One day he goes to the infirmary, witnesses two students do it, and the seme notices him but not the uke, ever since then he was informed by the seme where they'll do it so he can watchh ??
They have a toxic relationship , and I think the MC helps free the uke by the end..? I'm not sure if it was the end . . .

Also he has a friend that has a crush on him that muses at the end : that if he's so interested on watching them, why does he not realize that there is one near him :(

something just reminded me of this manga and I need to reread it, read it on 2018-19