Groper Train: From the Front and the Back (1981)

A middle school teacher who is cheating on his student's mother by playing molestation on the train, but is found out by her civil servant husband, and ends up swapping partners to apologize, and a story about a teacher who starts living with a woman he molested on the train, but then the mother shows up and the mother-daughter bowl is exhausting. A parody of Nikkatsu's "From the Back or From the Front."