A high school reunion. Among the men and women who seem to be excited about reuniting after a long time, a strange woman is present. Former classmates who are curious about the presence of this woman, open a chat app and start a meeting. What is the identity of the woman who blends into their memories? Is she an acquaintance they just forgot, or someone else? The high school's dark history they hid is being dug up. Exchanges happen in the real world, in a cafe bar, and in the virtual world, on SNS. At the cafe bar ODAZY, the second party of a high school alumni association is held. Classmates Akemi, Ryoko, Yoshioka, and Odashima are intimidated by the fact that a strange woman is present. While continuing the conversation, they have a meeting about the identity of the woman through a group talk on SNS, but the mystery only deepens. Eventually, the woman begins to talk about Akemi and Ryoko's dark history in high school, six years after graduating. Akemi and Ryoko were in the lower ranks of the school caste when they were in high school, and were ignorant of the class idol Yumi-chan. The two made an impersonation of Yumi-chan's personal account and repeated the unprecedented slander. Yumi-chan suffered from mischief without love, did not go to school, and disappeared. What is the true identity of the mysterious woman? Yumi-chan's twin sister? Yumi-chan herself? Akemi and Ryoko, who should have been "best friends", begin to curse each other while the suspicious demons are spreading. Yumi-chan's revenge begins ...