Heroic Purgatory (1970)

Rikiya Shoda is an engineer working for the Atomic Agency in Japan. One day, his wife Nanako returns home with a lost teenager called Ayu. A man, pretending to be the father, comes to get her back; Ayu keeps telling him that Rikiya and Nanako are her parents. Through this disruption, Rikiya suddenly starts remembering his youth as a revolutionary.