Psychopath Osananajimi to Kyonyuu Onna Kyoushi ni Sareta Ore ~Kako Kaihen de Yaritai Houdai~

Tsubasa is a new male teacher who just reunited with his old playboy childhood friend Tatsuya. Tsubasa tries to set him straight, but Tatsuya uses some kind of magic to turn Tsubasa into a young and attractive woman..! Totally bewildered by the turn of events, Tsubasa is helpless to fend off Tatsuya. Thus begins 'her' sexual training.. In no matter of time will Tsubasa's body, mind.. and even memory succumb to Tatsuya's technique. (Source: DLsite)