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I can't remember very clearly. But the seme is a teacher in school Indeed, he is a wolf {or sth like this, but not human} and Uke is a student. There was one scene where they had sex in the nursing room.

Seme seems to have to suck blood or have sex to increase his vitality.

There were other couple, the second seme hate first seme and wanna have sex with the glasses uke but end up had sex with other uke who bullied the first uke instead. This couple had their story.

Does the story sound confusing? Sorry for my English

It might be Yokubou no Shizuku (and its sequel Junai no Shizuku) by Higashino You.

A few words of caution: the main title has a number of gory scenes.

Omg thanks!!! I have been searching this for a long time 🥺🥺💕😭😭😭