Young Beast: Secret Pleasures (1978)

Yasuji Hajima runs a butcher shop. When he was younger, he was just as interested in the sex as the next man but lately he has a hard time satisfying his wife who is still oversexed at her age. The Hajimas have one son, Shuichi, who is studying to enter Tokyo University. It is after he sees his parents acting in which he considers an odious manner that he changes entirely and raises the roof in every whichever way.