Shijima has messy brown hair, which she styles into two short braids. Her turquoise eyes feature pale ivory accents, giving her a distinctive gaze. She wears a dark-colored blazer over a button-up shirt and dress, complemented by a ribbon bow tied around the collar. Her outfit is completed with dark socks, flats, and a pair of round glasses, enhancing her intellectual and mysterious appearance.

The original Mei, the student she was based on, has some notable differences from her supernatural counterpart. Unlike Shijima, Mei does not wear glasses or style her hair in braids. Instead, she has long, unkempt brown hair, which is a slightly different shade from Shijima’s. Mei is often seen wearing a hospital gown with a bandaged arm, suggesting a past injury or illness.

As a regular student, Mei wore the Kamome Academy middle school uniform, keeping her hair braided but without glasses, maintaining a simpler and more natural appearance compared to her supernatural counterpart.

At first glance, Shijima appears to be childish and cheerful, often seen smiling and displaying a seemingly warm demeanor. She can be empathetic, as shown when she offers comfort to Nene while she is captured. However, beneath this facade, she is sarcastic and cruel, exhibiting no hesitation in suggesting murder or making threats toward others.

Shijima has a strong interest in art, as seen in her introduction, where she is depicted painting. However, she has a self-destructive tendency, often destroying her own artwork in fits of frustration. This internal turmoil is reflected in her creations, as fabricated characters tend to crumble and disappear, symbolizing her dissatisfaction with her own existence.

With the reveal of the real Shijima Mei, it is shown that School Mystery No. 4 is simply an idealized, healthier version of Mei. Because of this, the two share several personality traits, such as their fascination with Nene’s ankles upon meeting her. Despite being deathly ill, the real Mei remains determined and optimistic, firmly declaring that she has “no intention of dying” even in the face of her inevitable fate.

Shijima is deeply protective and loyal toward the real Mei, as she was created from her original’s hope to live until tomorrow. Due to this origin, she is devastated by her own rumor and her inability to change Mei’s tragic fate. Over time, she has come to believe that fiction is meaningless, leading her to care little for her role as the 4th School Mystery. This existential despair makes her one of the more disillusioned and melancholic supernatural beings at Kamome Academy.

Shijima was created in the likeness of the real Shijima Mei, a former student at Kamome Academy. The original Mei was a talented artist who poured her emotions into her paintings, longing for beauty and perfection in her work. However, the exact details of what happened to Mei and how she became a School Mystery remain shrouded in mystery.

As School Mystery Number 4, Shijima uses her abilities to trap others within “painted worlds,” offering them alternate realities based on their emotions, regrets, or desires.

Number 4’s Powers
As the School Mystery Number 4, Shijima haunts the art room at Kamome Academy, where her painting resides. Her boundary is the Atelier Tower, which exists inside her painting, serving as the core of her supernatural domain.

Shijima’s unique power allows her to create entire worlds within her paintings, each one reflecting the wishes hidden deep within people’s hearts. The inhabitants of these worlds are also paintings she creates, appearing identical to their real-life counterparts. However, if the original painting of a character is destroyed, their picture-world version crumbles as well. It takes approximately 20–30 minutes for a new version to be reconstructed.

Once someone is pulled into her world, they are forced to follow her rules; otherwise, they will remain trapped indefinitely. The longer they stay inside, the more they begin to forget their original life, losing themselves within the fictional reality. The only way to escape is by finding the main character of the world and killing them. However, there is an emergency escape hidden within each world, though it is typically placed somewhere the main character can never reach. The location of this escape constantly changes, making it difficult to find.

Shijima has full awareness of everything that happens within her picture worlds and can respond immediately to any changes or threats, as shown when she reacted to Aoi and Akane spreading her rumor. Furthermore, any non-real humans within Kamome Academy can take on her appearance, suggesting that everyone within the picture world is either an extension of her or a clone she has created.

Cloning Ability
Shijima is capable of creating clones of herself by simply drawing them into existence. She primarily uses this ability to oversee her picture worlds and to avoid unwanted social interactions. However, her original self remains at the Atelier Tower, constantly painting. These clones retain reflections of her emotions and have a sense of identity, but any failed clones are discarded immediately.

Aspect of Control
The specific aspect Shijima governs within Kamome Academy’s supernatural system remains unknown, as her role as School Mystery Number 4 has yet to be fully explained. However, given her ability to create fictional worlds and alter reality, she likely represents the concept of creation, fiction, or artistic expression.

Shijima Mei’s existence as a supernatural being embodies themes of creativity, reality, and escapism. Her powers force characters to confront the question of whether they would rather live in a perfect illusion or face the struggles of the real world.

Her role as School Mystery Number 4 makes her one of the most philosophical and morally ambiguous supernatural beings in Toilet-Bound Hanako-kun. Unlike vengeful or power hungry spirits, Shijima simply seeks to create “perfect stories” even if it means trapping others in an eternal dream.