When the narrator arrives at school, he is greeted by his older sister, who tells him that he is welcome to stay with her and her friends. The older sister tells him not to worry about his younger sister's feelings for him. The narrator, however, does not want to be alone with his sister. He decides to go to his friend's house and wait for his mail. When he arrives, he finds that his friend, Yuko, has changed her dress. He also discovers that Yuko has sent him a message from her older sister. The message says that she has forgotten something important about the previous day's events, and that there is a video attached. He is horrified by the contents of the message and trembles at the sight of it. He trembles even more when he realizes that the message is from his class mates. He rushes off to find someone to show him their notes from the day before.