When Mikoto suddenly wakes up, she has lost her memory and is being held captive with an unknown man. She was detained by six girls called Ranna, Fumika, Riri, Yu, Rumina, and Murumuru who barricaded themselves in this tower to escape from the zombies. Although suspicions remain, Mikoto is released from detention and allowed to stay in the tower. However, the next morning, the man who was with Mikoto was found dead. The culprit is among these seven people!?

The culprit who killed the man is among these seven people! ? In addition to the marks of being hit with a blunt object, there is another mysterious scar on the corpse. The girls begin to share the information they each have with each other as they begin to suspect each other. Information about a group called followers and rumors about last night's mysterious singing voice. After they split up, Mikoto and Rana searched through their belongings and discovered what appeared to be a bloody murder weapon in a certain girl's luggage.

The barricade is destroyed and the zombies are allowed to invade, but the girls work together and manage to fight them off, but they notice that Rumina is missing. While everyone is looking for Rumina, Mikoto is attacked by a mysterious headache. Then, Mikoto begins to be confused by her own memories and secrets that begin to come back to life. Meanwhile, the girls find Rumina crouching and trembling in the theater sleeves. What secret does she have...

A vote is held to decide what to do with Tarumina, who was bitten by a zombie. The girls are divided over Rumina's treatment. Their suspicions about each other deepen, and the search for the culprit begins once again. Then, the seven people gradually begin to reveal their secrets once again along with their alibis. Finally, the voting to decide the culprit has begun.