Kōji, also referred to as Kori-chan, is a young ice demon from the Ice Tribe of the demon world. She is the younger sister of Yusa, though she has not yet reached adulthood and therefore does not possess a true name; Kōji is a temporary designation used for her. Physically, she is small in stature and resembles a mole. She has long ice-blue hair, black-blue eyes, a button nose, and no visible mouth on her face. Her clothing is a very light blue kimono. Kōji is a recurring supporting character who usually appears alongside her older sister. She demonstrates a strong sense of pride about her demon heritage and dislikes being treated as a low-class demon, and she has been shown to retaliate against Jashin-chan when Jashin-chan looks down on her. Kōji cares deeply for Yurine Hanazono, and her interactions with Jashin-chan are marked by a competitive rivalry. Her notable abilities are tied to her ice nature: she can produce shaved ice with her own powers, and her bodily fluids have unusual properties—her blood yields strawberry-flavored syrup, while her urine produces lemon-flavored syrup. Throughout her appearances, she remains a minor but distinct figure in the cast, providing occasional comic relief and demonstrating her ice-based talents.