The Demon
鬼畜 (original)
When Sokichi's abandoned mistress shows up on his doorstep with their three children, she is as surprised to discover he has a wife as his wife is to discover that he has a mistress.
Starring Shima Iwashita, Ken Ogata, Mayumi Ogawa, Hiroki Iwase, Miyuki Yoshizawa, Jun Ishii, Jun Hamamura, Keizo Kanie, Yoshi Katō, Mizuho Suzuki
Watch "The Demon" on Criterion Channel released in 1978. It's a drama movie, and has a rating of 7.4 out of 10 from Imdb which is usually fine for this kind of movie.