Eyes on Me by Toshirō Enomoto

5.20

After the death of his wife, Yukio has become more and more paranoid, believing that he is being followed and watched at all times. Yukio's late wife, before her death, was seeing and sleeping with another man. Not only did Yukio know about the affair, he would watch them have sex. Unbeknownst to his wife, his peeping on her became like a fetish. As the film progresses, Yukio goes to see a counselor to try and figure out his phobia and discover his deep repressed thoughts about his wife. In comes Akemi, Yukio's ex-girlfriend from almost a decade prior. Akemi is unhappy with her marriage and seeks the warm embrace of Yukio, which only furthers his descent into madness.