Ryoujoku Kyoushitsu

A run-down Tokyo at the end of this century. Here lives the young teacher Tsunagu who has to deal in his poor life with all sorts of bad-ass students and suffers a lot from his relationship with the violent lover Akira whose heart he knows he'll never have.
In spite of Akira's threats Tsunagu refuses to give up his teaching job because he wants to be there for a few good students like Aoitsuki. However, unknown to him, angelic-looking Aoitsuki isn't what he seems.
Meanwhile there is Shou ...
(from MangaUpdates)