Name: Eto 1st Mystery Ability: Time Manipulation. Can make people younger or older, or stop time. The Clock Keeper. Appearance: Orange hair, red eyes, Natsucolla uniform. Setting: Already dead, but attends Natsucolla School without being caught. Has a boundary; the boundary is a place of infinite clock loops. Personality: Straightforward and dry. Observant of her surroundings. Kind. Gender: Female

Name: Hinako 2nd Mystery: Hinako's Stairs Ability: Anyone who steps on the 3rd step of Hinako's stairs is taken to her boundary and turned into a doll. Appearance: Brown hair in low twin-tails, Natsucolla uniform. Setting: Already dead. Lurks in Natsucolla School. The boundary exists at the 3rd step of the stairs in the back school building; Hinako is at the top floor of the stairs. Personality: Sharp-tongued. Observant. Gender: Female

Name: Ponta 3rd Mystery: Mirror Hell Ability: Hands emerge from every mirror in the school to drag victims into the boundary. Appearance: Brown hair, Natsucolla uniform. Setting: Already dead. Lurks in the school. Personality: Cheerful. Ends sentences with "-su" (polite but casual). Gender: Male

Name: Puchipuchi 5th Mystery: The 4 PM Library Ability: Every day at 4 PM, a special archive appears in the library. Inside are books containing everyone's past and future. Choosing between red and white books—choosing red might lead to misfortune. Appearance: Brown hair, wearing an eyeball eye mask on his head, Natsucolla uniform. Personality: Funny. On bad terms with Hinako. Setting: Dead. Lurks in the school. Gender: Male

Name: Fuhaya 6th Mystery: The Reaper Ability: A powerful apparition related to death and boundaries, controlling the border between this world and the next. Appearance: Green hair parted in the middle, Natsucolla uniform. Setting: Dead. Lurks in the school. Personality: Kind and cares for his comrades. Gender: Male

Name: Yuan 7th Mystery: Hanako-san of the Toilet Ability: The power to grant wishes + manages the school's apparitions. The leader figure of the Seven Mysteries. Appearance: Black hair with red streaks, Natsucolla uniform. Setting: Resides in the 3rd-floor restroom. There is a traitor among the Seven Mysteries, and he is searching for them by stripping away their yorishiro (divine anchors). Relationship with Noa: Yuan -> Noa Often tries to protect Noa. She is his assistant. Gender: Male He teases and acts mean to her, but he actually treasures her deeply. Personality: Lazy. When Noa is in danger, he becomes seriously worried.

Name: Noa Appearance: Short pink hair with a cookie hair ornament, Natsucolla uniform. Setting: Yuan's assistant. The only one capable of stripping away yorishiro. Relationship with Yuan: Noa -> Yuan-kun Initially interacts with him as a "school apparition," but gradually comes to care for Yuan himself. As she learns about Yuan's past and secrets, she wants to help him even more. Species: Human Personality: Easygoing and kind. Gender: Female

Name: Tama Appearance: Short brown hair with pink streaks, Natsucolla uniform. Setting: Noa's best friend. The school's beauty queen. Constantly receiving confessions from Ponta, whom she rejects after giving him a score. Species: Human Likes rumors.