Age: 14-16
Loyalty: Keroro Platoon
First Anime Appearance: Episode 13
First Manga Appearance: Chapter 55

Koyuki is a foreign kunoichi who falls in love with Natsumi soon after coming to her home in Japan. She finds and rescues a stranded Zeroro and teaches him the ways of the ninja. After becoming a ninja, Zeroro changes his name to Dororo. She trusts Natsumi to teach Koyuki to live a modern life. She often wears a bow to tie back her hair and can instantly become a ninja. She shares a very close bond with Natsumi. Her skills as a civilian and a ninja are exceptionally outstanding and her athletic ability even rivlas that of Natsumi, making her one of the most physically powerful characters of the series. Despite having amazing powers and quite a hard and strict past, 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.