Hitozuma ryokô: Shittori midaregai (2011)

A woman loses consciousness on the roadside of a certain mountain pass. When she wakes up, she is sleeping in a room at the pension. But she doesn't know who she is. According to her caretakers, Tetta and Rui, she is Rin Komiya, who is planning to stay there. That night, Rin is lured by the moans that can be heard and ends up spying on the manager and his wife having sex. She can't help but put her hand between her legs and masturbate...