Kozuki is a slim young woman with green eyes. She has shoulder length blonde hair, and a blue headband decorated with two flowers.
She is extremely cheerful and has a crush on Hokusai Azuma.
She desires the title of "Black Fist" in the Kuroi family, and to do that she must steal something valuable enough to please their grandmother. As such, she joins the Professor for her own reasons. She and Minami Azuma gradually become friends and escape together at the end of part 1.
In part 2, she is seen protecting the ark with Minami Azuma but they ultimately fail and Ares takes it.
After they joined with the professor once again, she's left behind by the group because Minami does not want Kozuki to get involved in danger.
Remote Teleportation: Kozuki, by the Glowing Fish, has been given the ability to teleport. However, differently from Kyoutarou and Minami that can teleport themselves. She is able to send any objects or beings to different location, but she must firstly touch the target or pointing her hand to the object she wants to transfer. She is also able to summon them back to her. On particular occasions, she has also been shown to be able to teleport items without touching them.
Expert Fighter: She is also experienced in battle with bare hands. Her fighting style is almost identical to her sister.