Good Night Only to You.

After the death of his grandfather, Yoshisuzu Shougo moves into the mansion left to him. He lives there with Otosumi Youko, the maid. Shougo often has sex with Youko, but, while in the half asleep state following orgasm, he always sees a vision of a beautiful girl. The girl's name is Reiko, whose picture adorns a wall within the mansion.