She is voiced by Ryo Hirohashi in the Japanese Version and Luci Christian in the English Version.
Koyuki has long teal/dark blue hair that is usually tied in a ponytail, fair skin and green eyes.
She often wears a bow to tie back her hair and instantly become a ninja.
Koyuki is very carefree, optimistic, and eccentric for a normal Japanese girl, but believes in what is right and gets along nicely with her friends.
- Her Japanese Voice Actress, Ryo Hirohashi also voices Chane Laforet from Baccano!, Echo from Pandora Hearts and Kohina Ichimatsu from Gugure! Kokkuri-san.
- Her English Voice Actress, Luci Christian also voices Hiro Sohma from Remake of Fruits Basket, Mitsukuni Haninozuka from Ouran High School Host Club, Wrath from Fullmetal Alchemist, Medusa Gorgon from Soul Eater, Truth from Fullmetal Alchemist: Brotherhood, Alois Trancy from Black Butler II., Natsu Dragneel as child from Farity Tail and Train Heartnet as child from Black Cat and Cassandra Jill Warlock from Black Blood Brother.