The Five Mysteries of Grimoire High School

The Five Mysterious of Grimoire High School are a collection of five spooky urban legends that are said to be located within Grimoire High School.

While the school's Occult Research Club is aware of them, they admittedly do not know much more about them aside from the legends surrounding them. They also lament that, while other schools have "Seven Mysteries" their school only has five.

The five mysteries of Grimoire high school were the four girls from the MON and Lala, whose consciousness was also absorbed by Arbatel. Since the MON girls were assigned to capture the Grimoire in the Kayado Public Library due to its potential danger, the book perceived them as a threat. Because of this, it didn't let the girls roam free like the students, but had them play the roles of the ghost stories that roamed the school at night. However, since the MON girls and Lala were not wearing the enchanted school uniforms, they were excluded from the brainwashing from the start.

1: The One Eyed Hanako-san
"Every night they say you can hear someone crying in the girls' bathroom. A girl with a red skirt and a bowl cut, the toilet haunting Hanako-san. But here in our school they say she only has one eye."

2: The Science Room Formaldehyde Zombie
"The story of the girl who was captured by the crazed serial killer professor. They say after he tore her apart she was put back together as a zombie. The professor is long gone, but they say the zombie is still preserved in formaldehyde in the science lab where she's still hidden."

3: The Ten Meter Giant Girl
"If you just glance at the window you'll see a lone girl who meets your gaze. But wait, something's strange, isn't that a second story window?"

4: The Clone who Steals your Life
"You look at your reflection in the mirror and it's just your own face staring back. But wait, no, there shouldn't be a mirror here at all. And that's when the other "you" starts calling out "We look just the same, don't we? Why don't we just switch places?""

5: The White Haired Headless Girl
"Something drops down the stairs. A white ball? A girl comes searching for it and she just can't seem to find the ball, which of course she can't because the "ball" she was searching for was her own head."

Trivia

 * After hearing about the "Five Mysteries" Kimihito Kurusu quickly deduces that the "Mysteries" were actually Lala and the members of MON. This suspicion was confirmed in Chapter 76.
 * While the MON-team members had to play the role of the Five Mysteries, because Arbatel saw them as a threat, there is no clear explanation, as to why Lala was also part of the Mysteries. The most likely explanation was probably that Arbatel simply felt that due to her detachable head, Lala was just a perfect fit for the role in a fifth ghost story, and there was no particular reason.
 * The Seven School Mysteries (七不思議) is a common topic in Japanese schools and many schools across the country have developed their own sets of "Seven Mysteries" (usually created and perpetuated by the student body). The Mysteries are usually used to explain quirky misunderstandings (eg, that flight of stairs has one more step than normal, that statue just moved, there's music coming out of that empty room, etc) and act as tests of courage.
 * There are several re-occurring "Mysteries" based off of ghost stories created by successive generations of school kids:
 * The Mystery of a ghost playing Moonlight Sonata (a common musical piece taught in music class) after school-hours. The legend varies from the room just featuring the music, a haunted piano playing by itself or a visible ghost that either looks like Beethoven or a long-dead music student or teacher.
 * The Mystery of an anatomy model statue being so life-like because it is actually the body of a murdered student.
 * The Mystery of a statue coming to life in some fashion. The statue is usually of (a famous scholar & common subject of statues in front of Japanese schools) and he is often depicted running.
 * The Mystery of (Hanako-san of the toilet (トイレのはなこさん)), a girl ghost who haunts elementary school bathrooms.
 * A common punchline is for the seventh mystery to be that there are only six mysteries (with the "Mystery" being "Why are is it called "Seven Mysteries" when there are only six?").
 * It is not uncommon for schools to have an "Occult Research Club" devoted to studying these mysteries and other urban legends.