Koishi has wavy, green, short hair and dark green eyes, wears a black hat with a yellow ribbon around it. A closed, blue-purplish "third eye" is positioned over her heart, with cords wrapped around her torso and attached to each of her ankles. She wears a yellow-orange shirt with diamond-like blue buttons and dark green, frilled collar. The skirt is also green with a faint flowery pattern, but is lighter. Her socks are black.