Koyuki is an outsider kunoichi who meets Natsumi Hinata soon after coming to her home in Japan. She finds and rescues stranded Zeroro and teaches him the ways of the ninja. After becoming a ninja, Zeroro changes his name to Dororo. He trusts Natsumi to teach Koyuki to live a modern life. She often wears a bow to tie back her hair and instantly become a ninja. She is best friends with Natsumi. Her skills as a civilian and a ninja are exceptionally outstanding and her athletic ability even rivals 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.
Past
Episode 98 of the anime tells that Koyuki's entire past life before meeting Dororo or coming to Tokyo. Koyuki lived in a small hidden ninja village as a child and was only close to Mukuro, a fellow female ninja and Koyuki's childhood friend. In later episodes of the anime, the old chief of Koyuki's village is shown to be the leader of an acting troupe who play as ninjas for a theme park based based on ancient Tokyo. Koyuki seems to think of Natsumi as her best friend.
After moving into Tokyo, Natsumi met Koyuki as a new student in her class, but gets a quite odd first impression of her when Koyuki comes to her and says that Natsumi had "city scent". However, when Natsumi discovered that Koyuki was Dororo's partner, they began to spend more time with each other. Natsumi became both Koyuki's best friend and mentor to her about modern Japanese culture, as Koyuki hid in a secret ninja village throughout her life. She helps Natsumi in many situations, and vice-versa.
In the manga, Koyuki has a crush on Natsumi and several people are jealous of her. In the anime, she is still very close to Natsumi and enjoys hanging around a lot.
Koyuki and Dororo are both partners and good friends, since Koyuki's reason to come to Tokyo was to help Dororo reunite with his comrades, only to find that Dororo was most forgotten by the platoon, especially his childhood friend, Keroro. Koyuki first met Dororo (Zeroro back then) while still living in her ninja village, and there, Dororo learned the beauty of Earth and its nature, explaining his reluctant attitude towards the more Earth-threatening plans of Keroro. They live together in Koyuki's cottage in the forest (anime) / next door to the Hinata's (manga). Koyuki and Dororo have a very strong sibling-like bond, they obviously get along better with each other than Natsumi and the other platoon members. Koyuki seems to like Dororo a lot.
Mukuro was Koyuki's childhood friend and comrade back in their ninja village, but they were almost complete opposites. Koyuki was very carefree and friendly, while Mukuro was solitary and silent most of the time. When Mukuro tried to break free from her ninja customs and run away, Koyuki saved her from the punishment with her strong heart and loyalty to her. After being separated from each other when their village was permitted to go free, Koyuki never saw her old friend again, but at episode 98 of the anime, Mukuro walks past Koyuki and Natsumi, and smiles back at her, glad that she was still happy. Mukuro also gave Koyuki her name after seeing snow fall down when they meet.
Saburo is a close friend of Koyuki, and koyuki has strong feeling for him ,but natsumi gets jealous on how close they are and on how they have been together, she supports him in anything, in the Manga he gives her nicknames such a cutiepie or and goodlooking, they connect in the Anime, she likes to spend time with him, as does he, they are really close.
Giroro and Koyuki appear to have a fierce rivalry caused by Koyuki's tendency to hang around Natsumi and get too close to her, which causes Giroro to become extremely jealous and drive him to the point of fury. Often Giroro will address Koyuki as "that woman" and in one episode would have ruined Koyuki and Natsumi's pajama party were it not for the arrival of Dororo. However, despite such, both appear to have a mutual respect for each other and have even moved in perfect synchronization to protect Natsumi.
Apperance
Height: 156 cm (Start)/161 cm (End)
Weight: 44 kg (Start)/46 kg (End)
Blood type: AB
Trivia
It is unknown if Koyuki has parents.
In episode 330, she learns to make curry, but she puts slugs and newts in it.
She is very passionate about comedy and always enters the Doinaka beach Swimsuit Manzai Contest when she gets the chance
Etymology
Koyuki literally means "little snow" while Azumaya literally means "east valley".
