My Sex Report: Intensities (1976)

Akemi, a laboratory technician lives with her two younger brothers, one of whom is in the hospital in a paralyzed state. and the other one is doing illegal job of yakuza Hayato who is also their neighbor. She spends her evenings spying on Hayato as he makes love to his stripper girlfriend, Lily. Her voyeuristic attention points out her interests and Hayato suggests that she could be a great prostitute. It is not surprising that she agrees and directs her interests to this more profitable occupation.