Stepmother in Kimono: Stop It, Son! (2000)

Keiko becomes the second wife of Shizuo, the owner of a real estate company whose wife died in the Great Hanshin-Awaji Earthquake, through an arranged marriage. Despite the 20-year age difference, they are happy at first. However, as the company's financial situation worsens, their married life becomes colder, and Shizuo shows no interest in Keiko's advances. Around that time, Shizuo's son, Akira, who is not working much, begins to pressure Keiko into a physical relationship. Keiko, feeling lonely, accepts and becomes obsessed with sex. Then, when Keiko starts working part-time as an insurance salesman, Akira proposes that she murder Shizuo for the insurance money...