Midarana nikutai: Seikan jigoku (1985)

Yakumaru is researching an aphrodisiac to cure his impotence. He happens to meet Mitsuko, who also has an impotent husband, and Yakumaru gives Mitsuko the medicine he is researching. The next day, the two meet again to hear the results, but Mitsuko seems strange. Mitsuko, who was frustrated that her husband did not cooperate and did not take her medicine, ended up taking the medicine herself.