Bakuhatsu Sunzen!! Tenshi no Countdown

爆発寸前!! 天使のカウントダウン

Motoki is a junior-high student who can't ever concentrate on homework because of his sisters loud lesbian sex in the other rooms, he doesn't think life can get much worse.....until he gets a tutor and falls in love with her, from which he becomes a sex slave for her. (Source: Anime News Network)