Tsuchigomori Ryūjirou

Acts normal, caring and somewhat meek teacher in his human disguise, but is sarcastic, mischievous and quite short-tempered. He's also shown to be quite sadistic, having fun with threatening and scaring others. Dislikes people prying into his private life. has an odd sense of humor and likes to joke around, such as saying that he likes to eat human children, only to be met with terrified looks in response.

Despite him claiming that he only pretends to care about his students, he has been shown to actually genuinely care about them on various occasions.

When asked why he makes his teacher persona so different than his actual personality as a supernatural, he answers that it's simply because he feels like it.

Tsuchigomori is a tall, lanky man. He has spiky black hair with long white fringes and purple eyes.

When he disguises himself as a human, he looks almost indistinguishable from any regular person. In his true Supernatural form, he has noticeably sharper features such as sharp ears, claw-like hands and shark-like teeth; he also has four additional limbs protruding from his lower back.

He wears a white coat with a purple sweater underneath and golden eyeglasses.

As the curator of the 4PM Bookstacks, he has access to the entire body of knowledge surrounding the school, along with the present, past, and future. He seems to know everything about every student that has ever attended the school.

Even after his yorishiro and boundary were broken, his powers still allow him ways to retrieve the books in the library

He mentions that because of his position, it's possible for him to alter the future, but he does not plan to do so because any curator who does will be erased from existence..