Diary of Beloved Wife: Saucepot(2006)

Junko and Kohei were each other's first relationship, and got married. A white apartment, a white blouse, and white underwear; their relationship was pure. But then Junko put on conspicuous lingerie and a black dress, and went to attend a class reunion. Suspicious, Kohei followed behind her until she disappeared into a hotel with Okada, a former junior high school classmate. Kohei had learned from his mother to obsessively despise `filth,' and vowed to make Junko utterly filthy. So, he presented his own wife to a gang rape club...