Koyuki is a main character of Ginga Densetsu Anju To Jiromaru.
Just like her mother, she's white and has blue eyes.
As a puppy Koyuki caring and considerate when she begins to worry about her brother Jirōmaru and shows when she followed her siblings to find him.
Koyuki lives together with her mother, her siblings, and Anju and her grandfather. One day, Yuki and Yoshito Sawamura do not return. A few days later, Yuki hobbles home in bad shape and dies of her injuries soon after.
After this Anju's uncle, Shinjirō, comes in and forces Anju to leave. Jirōmaru goes after Anju, but Koyuki and Saburōmaru are left with Tarōmaru at home.
Tarōmaru leads his siblings to the place where Yoshito Sawamura and Yuki's accident occurred. There they meet Jirōmaru, Anju, and Seisaburō. Shinjirō comes in with a gun and shoots at Anju and Seisaburō. Jirōmaru jumps between Shinjiro and Anju, dying in front of Koyuki and the others' eyes.
19 years later Koyuki is still alive and Anju greets her.
- Although Koyuki and her siblings are around the same age as Weed's puppies, at the end of the story she and her two remaining siblings are much older. This is a mistake on Yoshi's part, probably due to the fact that the dogs in GDATJ were not originally intended to be related to Gin and his family.
- Some fans believe that the father of Koyuki and her siblings is a mix or a non-Nihon Ken, as Jirōmaru is a non-brindle yet silvergrey.