Koko Zenibako is one of the Humanoid Shuuki who resides in the Hidden Village. She became a Humanoid Shuuki due to the Peach she ate mutating her. In her human form, Koko was a rather petite young woman with short hair and small eyebrows. After becoming a Humanoid Shuuki, her hair turned white, and she gained gold eyes as opposed to their usual color. She grew one horn on the right side of her head and black marks under her eyes. It is noted that Koko is dressed in the same skintight outfit as other Humanoid Shuuki. Koko is rather bubbly and lively. During her first encounter with both Himari and Shushu, she openly called her name to them, seemingly without realizing it, then wondered how both of them knew what her name was. She cares a lot about her friends and allies, healing Yuuki, Aoba's younger brother, by using her powers and being irritated after seeing the scars that were on Naon. In comparison to Aoba and Naon, Koko is almost like the younger sister among the trio.