The black uniforms are characters from the "Blue Archive".
He is a member of Gematria, a mysterious organization belonging to the outside of Kivotos. According to him, he is an observer, a seeker, and a researcher. As the name suggests, he wears a black suit, and his body is black and inorganic like a shadow. He also wears black gloves on his hands, but there are cracks on the ground between the gloves and the sleeves of the suit. The same cracks exist in the area between the gloves and the sleeves of the suit. The name "Kurofuku" is a provisional name given by Hoshino because of his appearance, but he likes to call himself that, and is also called "Kurofuku" by the members of Gematria. His original name is unknown. His polite and optimistic tone of voice, combined with his appearance, gives him an eerie atmosphere. Her first appearance is in the main story Vol. 1, "The Countermeasures Committee. He is a collaborator of the Kaiser PMC board members who tried to take away Abydos High School by forcing the school to take on a large debt. He is the first member of Gematria to appear in the film, and like the Kaiser PMC board member, he is the first "bad adult who exploits children" to be depicted in the film. In the "Countermeasures Committee" scenario, an "adult battle" is depicted in which he and his teacher argue over Hoshino, the supreme mystic of Kivotos, whom the black-suited man is seeking to take into custody. Later, he reappears in a pre-battle commentary scene in a general battle of the Decagramaton system. It seems that the fact that the teacher, who is not a gematria, is chasing after the decagrammaton is not a pleasant situation. However, she seems to like him and wants him to become one of Gematria's friends rather than an enemy. According to Beatrice, the black-clad man believes that the teacher "recognizes him as a friend and that they can compete with each other.