Yugi Amane, better known as Hanako, is a ghost in the building of Kamome Academy who grants wishes and governs over the Seven Mysteries as School Mystery Number 7. He had took his own life after killing his own younger brother when he was still a first-year, his guilt overwhelming him. Being the seventh school mystery and the leader of the Seven Mysteries, Hanako maintains the balance in the relationship between humans and supernaturals of the school, and is often seen helping others around and protecting the school. Hanako is cheerful, outgoing, and likes having fun. As a ghost, he is rather mischievous, then he enjoys teasing others and can be very playful and pranky. Hanako has short hair having straight bangs falling over his eyes. Hanako wears the old Kamome Academy male uniform.

Yashiro Nene is a cheerful, outgoing, and earnest girl who is a hopeless romantic and deeply insecure about her appearance. She is kind and friendly, but can be naive and reckless when trying to help others. At the start, Nene goes to her school's bathroom and calls on "Hanako-san" to grant her a wish for love. She finds out Hanako is actually a boy. After a mermaid scale curse mishap, Nene makes a pact to work as Hanako's assistant to pay off her debt. Because of the mishap, she turns into a fish when fully submerged in water due to a mermaid scale curse. Nene is a 15-year-old first-year high school student with large magenta eyes and cream-colored hair going into a gradient of soft green. She also has two dark brown magatama hairpins on the side of her head.

Kou Minamoto is a 15-year-old cheerful, brave, and kind-hearted junior high student with a strong sense of justice. Though loud and prone to rushing into trouble, he is deeply caring, fiercely loyal to his friends, and surprisingly domestic. As part of the Minamoto exorcist clan, he initially believes all supernaturals are evil, but he is open-minded enough to change his views and befriend Hanako. Kou has short spiky orangey-blonde hair, light blue eyes, and two sharp protruding canine teeth. He wears a red traffic-safety omamori amulet worn as a piercing on his right ear. He carries his spiritual staff, which looks like a plain black umbrella when disguised.

Aoi Akane is a first year student at Kamome Academy's High School division, and the Student Council's Vice President, as well as Aoi's childhood friend with whom he has an obsessive crush on. He is also classmates with both Aoi, Guest, and Nene at Class 1-A. He is secretly a Supernatural who controls the Present as the Guardian of the Present, one of the Three Clock Keepers along with Kako and Mirai, and thus, is one of the Seven Mysteries of the school. Both Akane's hair and the irises in his eyes are reddish-brown in color, with his eyes having teal-colored pupils. Akane normally wears a pair of rectangular glasses. As a Clock Keeper, Akane has an Automaton Clock, which like the others, is gold in color with a chain and a tassel attached, which he uses to stop time. He sometimes carries a bat with several crooked nails, which he uses to hit people.

Akane Aoi is a first year student at Kamome Academy's High School division and is Guest's and Nene's best friend. She ususally introduces supernatural rumors to Nene which helps Guest and the others find and defeat the curses. Aoi is a petite girl with indigo hair and eyes. She keeps her hair tied up into two looped pigtails that look like perfect circles behind her head. Aoi is a sweet and cheerful person. Although she claims to dislike scary stories, she continues to delve into them for the sake of cheering Guest up, since she knows that Guest enjoys them. Aoi cannot see supernatural spirits unlike Nene and the others.

Tsuchigomori is the School Mystery Number 5, featuring a tall human disguise, a spider-like supernatural form, and a grumpy yet protective teacher persona. He has spiky black hair with long white side fringes/highlights and deep purple, tired-looking eyes. He works as a science teacher and homeroom teacher at Kamome Academy. He governs the Fifth Mystery known as "The 4 PM Bookstacks," an archive containing books that record the past and future of every student.