Kōbai Yukiyanagi is a former Agent of Winter who appears in the backstory of Agents of the Four Seasons: Dance of Spring. She was the winter deity’s human vessel before her daughter, Hinagiku Kayō, became the Agent of Spring. Kōbai fell in love with Shungetsu Kayō, the previous Agent of Spring, and their relationship resulted in Hinagiku’s birth. Because she was an Agent, no one could openly criticize her, but she was nevertheless called a disgrace to the name of the Agents. Shungetsu’s legitimate wife treated her terribly, and in order to shield Hinagiku from that harassment, Kōbai was rarely at home. Ultimately, she took her own life. As a Winter Agent, Kōbai possessed the power to freeze life itself, and like all Agents, she underwent a Season Descent alongside the then-Agent of Spring. Her tragic fate and the circumstances of her relationship with Shungetsu are a key part of Hinagiku’s past, shaping the current Agent of Spring’s feelings about love, duty, and the cost of carrying a season. Kōbai’s story is told only through flashbacks and references, but it provides crucial emotional weight to the main narrative.