Souta, who secretly had a crush on Yosuke's beautiful young stepmother, Saki, realized he had left his smartphone on the way home from visiting Yosuke's house and went back to get it. The door was unlocked, so he went to Yosuke's room and witnessed a scene he couldn't believe his eyes: Saki and Yosuke were having sex. Souta couldn't believe that Saki , the Saki he had admired, was in a relationship with Yosuke... Souta was filled with anger at the mother and son who had made him feel this way, and swore to take revenge.