Eleven years before the series began, she and her husband, Taiko , were assassinated by a mysterious man who wore a mask. Later on, it is revealed that one of the Fuuma brothers killed her, but that her death was never planned. She was only assassinated because she tried to defend Taiko.
Koyuki and her husband, Taiko, had a loving relationship. They openly expressed their appreciation and care for each other through amiable arguments that would end in hugs and verbal declarations of love. These declarations of love almost appeared to be heated arguments.
To Taiko: “Say, you came home so late tonight! You work too much!! I’m really worried!!”
To Taiko: “You’re always thinking about your squad members! You must be exhausted!! You have my respect!!
To Taiko: “I. Love. You!!!”