Koyuki is a frail young lady. She has black hair which was always tied into a bun fastened with a hair pin. Her hair was decorated with a kushi (hair comb) and a three flowers hairpin. Koyuki had big eyes with flowers in them. She wears a circle patterned kimono tied with an obi.
Kind, sad, thankful for the help, She was gentle and was grateful for Akaza since he was looking after her, most of the time. She would get emotional and cry when having a normal conversation with Akaza as it reminded her of hope and that that there are many opportunities to do the things she never got to do.
She was born very sick, and because of this, her mother drowned her self not wanting to see her baby die. But she was able to live with the help of Akaza and her father, Keizou. Two years later, she got well and was engaged to Akaza.
However, she was poisoned after drinking water from the poisoned well and passed away at the age of 16 years old at the same time as her father, who had also died from drinking the poisoned water.