Kôkô kyôshi: shisshin! (1985)

A female teacher Kumi Yamamoto was raped by a man who attempted suicide. During Kumi's class, a woman in a miniskirt suddenly entered the classroom and shouted, "Is Yuichi Kobayashi's son here?" Yuichi Kobayashi was the name of the man who raped her. The woman in the miniskirt was Maria, a debt collector, and she had come to find out where Yuichi was, calling for his son, Kotaro. Kumi learns that Yuichi is on the run from his debts. Yuichi tries to have sex with Kumi again, but she vehemently rejects him. The next day, as Kumi is comforting Kotaro, the biology teacher, Saiki, enters the classroom and makes advances on her. Kumi calls Yuichi and demands sex from him. Meanwhile, Kotaro succumbs to Maria's temptation and becomes addicted to sex.