A tomboyish girl who was Jing's close friend when he was young. Cassis talks and dresses as a boy so that the Spirit of the Forest doesn't know she is a girl. She has a virile and strong personality, has long blonde hair, which she somehow managed to hide inside her cap, and uses a baseball bat as a weapon.

Cassis has feelings for Jing, but can't be honest with him. After Jing's birthday party, she is kidnapped by the Spirit of the Forest, and her rescue was Jing and Kir's first adventure as a duo.