The Sex Pervert(1977)

Masao Nishimura is a cheerful young man who works at a pastry shop. But he has another face. At night, Nishimura peeks out his favorite telescope from the window... He is obsessed with Kyoko, a clothing store clerk. He followed Kyoko's life without missing a single moment... Based on a true story that happened in Osaka, where a lively and cheerful young man confined and assaulted a woman.