Number 3

An unnamed supernatural who formerly represented Kamome Gakuen's 3rd School Mystery, the Hell of Mirrors.

Appearance
Number 3 seems to be a bird-like supernatural. While inside the mirror, its silhouette is of a shadowy figure. Its face protrudes through the mirror, showing a bird mask with one right eye with a marking on the forehead. It possesses two disembodied human hands with long nails in this state, used for gesturing.

When forced outside of the mirror by Tsukasa, it appears to be a giant bird with human arms. It wears a dark cape with a light, quilted underside. On the cape are several decorations, with circular and square shapes. Its arms are covered with fabric, only exposing past the wrist, where there is feathers, making it look similar to wrist cuffs. It has fully humanoid hands. There is a band on its right leg.

There is a visible scar on its left eye.

Personality
The supernatural is quick to mock those who appear before it, using their own insecurities against themselves. It is believed those with a completely pure and brave heart will return untouched. This is shown when the supernatural assumes the form of Aoi to mock Nene of her "radish legs".

He is a deep narcissist who scores people giving Mitsuba a 7 and Nene a 4 (out of an unknown scale), but insulting them over their flaws. He can be seen as sadistic due to his penchant for torturing others with their insecurities. He dislikes when people struggle against him.

Number 3's Powers
Its powers rely on it reflecting back the person's insecurities and varies depending on the person.

It has command over the Number 3's boundaries. As such, it can shapeshift or morph the appearance of the boundary as they see fit to torment the individual. It is also able to summon mannequins from the mirrors to fight.

The true extent of its powers are unknown, as he was easily destroyed by Tsukasa, which serves more as a testament of power for the latter. However, Hanako himself stated he did not want to enter the Number 3's territory only out of concern that his mere presence could cause the territory to change and make it more dangerous for Nene. Thus it can be implied the Number 3's actual strength wasn't anything formidable.