Yumi marries Tatsuo, a successful businessman, and becomes his second wife. Tatsuo’s son, Yasuo, struggles with the nightly sounds of intimacy between his father and stepmother while studying for exams, leading him to secretly observe them. The following morning, overwhelmed, Yasuo asks Yumi for a single embrace, but she refuses, citing his exams. Later, Yasuo delivers condolence money Yumi asked him to give to Akemi, a widow grieving her husband. Akemi, alone and distraught, engages in self-pleasure before her husband’s portrait. Yasuo witnesses this and offers comfort, leading to multiple climaxes for Akemi. Subsequently, Yasuo meets and has sex with Emi, a married woman he found on a dating site. It is revealed that Yumi, Akemi, and Emi are sisters.
