Kurofuku is a young, fairly tall man with purplish-blue hair that covers his left eye, dressed in black clothing, a simple fact reflected in his name. He serves as a staff member at the secret research laboratory that experiments on magic users. His personal history prior to his employment at the facility is largely unknown.

He is characterized by a reserved and obedient personality, consistently following orders and putting his best effort into completing the tasks assigned to him. Despite his loyalty to the organization, he is described as once feeling carefree about the magic users, such as Yuki, hinting at a capacity for warmth underneath his dutiful exterior. His superior, Chisato, acknowledges him for his brilliance, suggesting he possesses a sharp intellect or notable competence in his role.

Kurofuku’s primary motivation is to carry out his missions as directed by the laboratory. In the story, he is placed in charge of the magic user Nanami and later becomes involved in the pursuit of escaped B-rank magic users. He is given a final opportunity to recapture them by using the foresight ability of Mizuka, another witch, but the operation ends in failure. This failure leads to his dismissal from the laboratory and, soon after, his assassination. His key relationships include his oversight of Nanami, his collegial bond with Chisato, and a working partnership with Mizuka. He does not display any supernatural abilities of his own, functioning instead as a human operative whose value lies in his intelligence and reliability. His narrative arc is brief and ends with his downfall and death after a single critical mission goes wrong.