Kyōsuke Yotsuya, a young boy with short black hair and striking golden eyes, favors casual outfits adorned with animal motifs. As an elementary student, he stands shorter than his older sister, Miko, with whom he shares a tight-knit bond rooted in shared routines like watching television, shopping for their mother’s gifts, and childhood moments of bathing together—a testament to their familial intimacy.

Driven by a mistaken belief that Miko might have a boyfriend, Kyōsuke harbors a protective streak, often shadowing her discreetly to shield her from perceived dangers. This vigilance inadvertently draws him into supernatural encounters, such as innocently handling a cursed snowman figure, unaware of the lurking ghost until Miko’s urgent intervention saves him. His determination to guard her clashes with his obliviousness to her spirit-seeing ability, unknowingly fueling her stress.

Curious yet occasionally bashful, Kyōsuke flusters easily, as seen when a shop worker’s questions about gift choices leave him tongue-tied. His concern for Miko sometimes manifests awkwardly, like bursting into the bathroom during her bath to search for nonexistent signs of abuse—a misguided but earnest attempt to ensure her safety.

His name, blending the Japanese words for "respectful, polite" and "help, assist," mirrors his courteous nature and role as a supportive sibling. Living with his mother and sister after their father’s passing, Kyōsuke’s narrative centers on his dynamic with Miko, navigating both mundane family life and unseen supernatural tensions.