向後 千夜美

She is the grandmother of a student at the cram school where Naito teaches. She takes care of her granddaughter in place of her daughter, who is busy traveling abroad. Her husband passed away a long time ago and she has been single for just as long. In her younger days, she was a sexually uninhibited, and a well-trained promiscuous pervert. When she got married she took the opportunity to play the role of a chaste wife. [From official site]