Koyuki was the daughter of Keizo. Due to her sickness, she spent most of her time bedridden while being treated by Hakuji. Koyuki was a frail, fair-skinned young lady with large, rounded pink eyes with white pupils shaped as flowers. She had black hair which was always tied into a large bun fastened with a hairpin and decorated with a Kushi (hair comb) and three snowflake hairpins. Koyuki wore a circle-patterned, pink kimono that faded into a snowflake pattern tied with an obi. Koyuki had a kind and gentle personality, showing much gratefulness to Hakuji during his time looking after her. She would get emotional and cry when having normal conversations with him, especially concerning his reassurance of returning to the annual fireworks show, as it reminded her of hope and that there were many opportunities to enjoy the things she never had the chance to enjoy.