Earobi seikan: Mucchirina oshiri (2003)

Rumi is a rookie office worker who is hopeless at her job but popular with men. One day, her uncle Inuma, a businessman, asks her to take on a special assignment: posing as a married woman living apart from her husband, she is to sign up for an aerobics class. Upon arriving, she walks in on the owner, Akemi, and the instructor, Hideo, in a compromising embrace. Hideo is instantly aroused by the sight of Rumi, while Rumi finds herself the target of Akemi’s jealousy.