Kaoru Hatsushiba, a junior high school student and classmate of Sunao Moriyama, possesses black hair and black eyes. He is consistently portrayed as the close companion of another classmate, Mudou Kirihara, frequently supporting Mudou's attempts to interact with the creature Potemayo. Exhibiting a sympathetic disposition, Kaoru visibly reacts with pity to Mudou's recurring misfortunes and injuries, often uttering "Mutan" in a tearful manner. His primary role involves providing steadfast emotional support to Mudou amid these comedic mishaps. Kaoru harbors romantic feelings for Mudou, extending beyond friendship, though Mudou remains entirely focused on Potemayo, resulting in unrequited affection that subtly underpins Kaoru's interactions. A distinctive physical feature noted is his "ugly lips." Beyond school, Kaoru's interests include films, citing Brokeback Mountain and Alexander the Great as his favorites. Across the series, specials, and other media, his character maintains a consistent presence within the classroom dynamic centered on Potemayo and Guchuko, without significant development or backstory expansion.