Souta, who was secretly in love with Yosuke's mother-in-law, Saki, who is young and beautiful, realizes that he forgot his smartphone on the way home from visiting Yosuke's house and returns to retrieve it. When she went to Yosuke's room because the door was unlocked, she could not believe her eyes and witnessed Saki and Yosuke having sex. To think that Saki, who she admired, would have a man-woman relationship with Yosuke more than anything else... Souta got angry at her mother and child who made him feel this way and vowed her revenge.
