Nishimachi Shinryoujo no Himitsu - The Secret of Fuyuki

A junior high school English teacher named Kurei becomes instantly smitten with a young, attractive doctor at a nearby clinic. Fuyuki, the doctor, is inexperienced and in need of assistance, so he asks Kurei to help out at the clinic. Their relationship develops rapidly, but Kurei soon becomes concerned when he observes unusual patients arriving and departing, leaving Fuyuki visibly drained and fatigued.