Kōji, who also goes by Kōri-chan, is a young ice devil with long ice blue hair, black-blue eyes, and a button nose that is sometimes depicted as black. She has no visible mouth and a face resembling that of a mole, leaving her unable to speak. She typically wears a very light blue kimono.

She dislikes being seen as a low-class demon and has retaliated against those like Jashin who treat her as such. Yurine Hanazono maintains a positive relationship with her and has aided her in conflicts with Jashin. She consistently shows fear toward Mei Tachibana, who often kidnaps her for her collection.

Biologically unique, her blood produces a strawberry-flavored syrup and her urine a lemon-flavored syrup. She is approximately one human year old and is the younger sister of Yusa, a yuki-onna who cares for her and sells shaved ice.