Zoku mibōjin geshuku: omote mo kashimasu ura mo kashimasu (1975)

A young man named Jun Umemura, with the look of a radical student, arrives at the boarding house run by widowed 'Mama' Katsu. Struck by his handsome features, she showers him with attention and gradually coaxes him into her bed. But just as he's faced with Mama’s seductive, bare body, he spots a fellow activist ... and bolts out the door.