Bite Into Me(2017)

Midara na Kimi ni Kamaretai

A high school freshman visits a former teacher of his who has become a shut-in. This teacher, a beautiful and doting woman, got him through middle school by providing moral support, but gave up teaching and has led a life of reclusiveness ever since. By accident, he catches her drinking blood and having an aversion to light, lending to the possibility that she may have become a vampire.