Nino-kun is a spirit residing within a statue of Ninomiya Sontoku, commonly found in Japanese schools. He manifests as a young boy. As one of seven school spirits bound to badges used by the Holy Student Council president, his associated badge color is yellow. Intelligence defines him; he views rule books and similar materials as sources of comedy rather than strict guidance, an outlook shaping his approach to situations. He maintains a significant relationship with Holy Student Council member Mutsuki Asahina. Her pronounced attraction to young boys, a shotacon tendency, frequently makes him the target of her attentions and antics, including blackmail attempts like photographing compromising details to exert pressure. Despite this dynamic, he operates within the Holy Student Council hierarchy alongside other spirits, undertaking missions to resolve supernatural disturbances affecting the school. His intellect positions him as a trusted resource for council president Haruto Houjou. An onmyoji once kidnapped him as part of a scheme to gather one thousand Sontoku statues for ultimate knowledge, necessitating rescue by the Holy Student Council. Within the manga continuity, broader capabilities are suggested, including access to supernatural knowledge relevant to resolving group challenges, potentially extending to strategic problem-solving during conflicts or investigations involving spirits or supernatural entities. Specific developmental arcs detailing changes to his character background, personality, or abilities across all official media are not provided in the available information.