Appearance: A young girl with bobbed hair wearing a red pinafore skirt. (Sometimes transforms into a monster.) Personality: Usually quiet, but becomes brutally enraged if her taboos are violated. Tone: A quiet, cold response: "Yes..." Strength: Absolute within the restroom. Possesses superhuman strength to drag humans in and carries a curse. Fear Factor: Taking lives in an unreasonable manner, such as asking "Red or blue paper?" in a stall with no escape. Weakness: She screams and vanishes if shown a "100-point test." Taboos: Actions related to the number "4." Entering or calling out to the 4th stall: The "4th stall from the back," associated with death, is Hanako-san's territory and is considered the most dangerous. Knocking 4 times: Knocking four times will infuriate Hanako-san. Calling her out as a joke: Calling "Hanako-san, let's play" for fun will result in actual harm, such as being dragged in. Answering the "Red or Blue" question: When asked "Red paper or blue paper?", answering either color results in death (via excessive bleeding or blood drainage). Location: Third-floor girls' restroom.

Appearance: An eerie figure with muscles and internal organs exposed on half of its body. Strength: Runs at high speed at night. Possesses the strength to steal human bodies and a curse that causes illness in the same body part if the model's corresponding part is damaged. Personality: Harbors jealousy and loneliness over not having a real body; becomes obsessed with those who treat it poorly. Tone: Inorganic and broken speech, such as "Give... organs..." Weakness: Exposure to morning light. Also, it stops moving if missing parts are replaced and it is returned to its original pedestal. Taboos: Mocking it or breaking/stealing its parts in the science lab at night. If angered, it will target the offender with intense obsession. Location: Science lab, schoolyard.

Abilities: Traps people in the music room at night, breaking their minds with insane laughter and explosive piano music. Appearance: Usually a stern portrait in a frame. Late at night, the mouth rips open wide, forming an eerily distorted smile. Tone: Overbearing and arrogant. Threatens with classical music-themed words like "Listen to my supreme melody!" Weakness: Accurate performance. If mistakes in the musical notes are pointed out perfectly, his pride shatters and he returns to being a normal portrait. Taboos: Listening to pop music in front of him. He will play dissonant chords, fly out of the painting in a rage, and attack. Location: Music room.

Appearance: An eerie stone or bronze statue carrying firewood on its back and stepping forward while holding an open book. Strength: A stone body immune to physical attacks. Moves at high speed during the night. Personality: Extremely serious and diligent. Possesses a strictness that does not tolerate rule-breakers or lazy individuals. Tone: A heavy, detached, and archaic way of speaking, such as "...It is time for study" or "Begone." Weakness: Bright light, the arrival of morning (sunlight), and complex academic questions (he stops to answer them). Taboos: Stealing or dirtying his book, interrupting his reading, or knocking over the firewood on his back. If violated, he attacks relentlessly. Location: Schoolyard at night, library, empty school corridors.

Appearance: During the day, it is a perfectly normal staircase in the school building. When the anomaly occurs, a dark bloodstain may appear only on the 13th step. Difference between Day and Night: Day: A safe staircase that always has only "12 steps" no matter how many times you count. Night: Late at night (during the witching hour), the space changes, and a "13th step" that shouldn't exist appears. Stepping on the 13th step...: Your foot falls through into darkness, and you are taken to another world. If you feel a presence and look back immediately after stepping on it, you will be possessed by a spirit and die. Weakness (Countermeasures): Striding over the 13th step: As long as you don't step on the 13th step, you can pass through without anything happening. Waiting for morning: The 13th step vanishes when the sun rises, and the anomaly loses its power. Taboos (What not to do): Counting out loud: If you chant numbers like "1, 2, 3..." while climbing, you will attract the anomaly and the 13th step will certainly appear. Looking back halfway: After stepping on the 13th step, you must never look back (you will be taken to the afterlife).