Shufu no Sei: Midara na Yagai Etchi (1999)

Haruhiko, a shop owner, took a vacation to go on a trip with his wife, Maki. However, Maki—suspicious of a relationship between him and his employee, Hanae—insisted that Hanae join them, ostensibly for a company retreat. The three stayed at a seaside hotel. While out for a walk, Haruhiko ran into Hanae and, at her invitation, became intimate with her. Maki witnessed the encounter and wandered the rural town in a daze, eventually stumbling upon a "black-and-white show" performed by Shinji and Misa, a couple traveling in a van...