Even among the eccentric arcanists of the Apeiron School, she is considered an outlier. The youngest Prime and a massive genius, she is solely interested in the abstract world of numbers. Her human sensitivity is very weak, to the point where she proves a person's number before they can even discover it themselves.

Because of this, Sophia considers 37 a precious friend but finds her difficult to deal with. This seems to be influenced by her mother, who was equally high-handed and cared for nothing but logic and numbers.

As an example of how 37 differs from typical believers, unlike their obsession with numbers, she holds no animosity toward irrational numbers.

She detests beans to an extreme degree, being reluctant to even approach a table where beans are placed, and dislikes all food and drinks made from beans.

It is mentioned that her hair is severely curly and often gets tangled.

The leader of the Apeiron School. The number 6 signifies harmony within the school and is regarded as a perfect number; it is said to be granted to the school's leader through generations.

He reads frequently and is taciturn. As the leader, he presents a strict and rigid image of a principled man. However, while he values principles fundamentally, he is the type to exercise as much flexibility as possible within those bounds.

His hair ornament was a gift from Sophia as a token of gratitude for his help when she first moved to the island. 37 suggested making it a hair ornament to fix his hair, and when 210 saw them trying to make it a cone shape, he stopped them, resulting in its slightly angular circular form. Consequently, it is a collaborative work of 6's three closest friends.

6 also keeps the ornament polished and cherishes it. However, since seagulls frequently fly into his room and steal it, he reportedly has to go and retrieve it himself every time.

A practitioner of the Apeiron School. The only verifier on the island and the person in charge of matters related to the phenomenal world (the outside world). Having come from the phenomenal world with her parents as a child, she is more familiar with it than other members of the school.

According to the island's rules, a number becomes one's name upon discovery, but since she has not yet found her number, she still retains her name.

Her medium for arcanum is a brass ruler she carries at her waist, and her described abilities include minor arcanum such as restoring messy spaces to their original state.

A practitioner of the Apeiron School and a self-proclaimed rhetorician. He is characterized by the grapevines decorating his hair.

Within the school, he shows primary interest in linguistic expression and is seen using eloquent phrasing during heated speeches or conversations. He prefers the title 'Rhetorician' over the name 210. Perhaps because his academic leanings are so distinct, he is often seen bickering with other figures in the school, led by 37.

Though he spends the entire story being sarcastic, nitpicking, and arguing, it is revealed that this is merely his way of eliciting debate and he harbors no personal ill will. However, 37 openly dislikes this method of his, claiming it is grand only on the surface and lacks substance.

He consistently calls 37 "The Star of Hermes." 37 does not like the title, claiming she doesn't understand it.

He has been childhood friends with 6, 37, and Sophia since they were young.