Nishimachi Shinryoujo no Himitsu - The Secret of Fuyuki

About a junior high school English teacher, Kurei, who falls in love at first sight with a beautiful, young doctor from the local clinic. Inexperienced and short of help, the doctor, Fuyuki, recruits Kurei to help him at the clinic. The two grow close quickly, but soon Kurei notices some mysterious patients that visit the clinic and leave a drained and exhausted Fuyuki.
(Source: M-U)