Assault! (1976)

A bar-owner named Kuroki, forlornly waits for his adulterous wife to get back from messing around with her boyfriend. She returns, but because she's been fooling around with gangsters she brings trouble with her. Kuroki gets tied up and beaten, his wife and customers get tortured and raped, and it is finally up to the mousy cuckold to set things right, Straw Dogs-style.