Yuki serves as a guardian angel and is the reincarnation of a white snake from her previous life. As the oldest and highest-ranking among the twelve guardians, she carries a Senior position. In her past existence, she lived as a pet snake in a shrine frequently visited by a young Gorō Mutsumi, who saw her as an older sibling. After moving away, Gorō promised to return during winter break. When he arrived, the shrine was engulfed in flames. While trying to save the priestess, he was rescued from the fire and smoke by Yuki’s spirit—the snake had already perished in the blaze. Her death by burning left her with a lasting fear of fire.

Her demeanor is gentle, warm, and thoughtful, often assuming a caretaker or motherly role toward the younger angels. Though typically quiet, she offers meaningful advice when consulted. She is widely regarded as kind, respectful, and good-hearted.

As a guardian angel, her signature color is blue, and her name, meaning "snow," reflects her white scales and pale complexion from her serpent form. She is linked to the Four Saint Beasts and is destined to become the bride of Gou, the Azure Dragon.

In the second season, after the previous goddess breaks a rule, Yuki is selected as her successor. In this new role, she gains greater power and a stronger resolve to join the sage’s dream. Her chief responsibility becomes overseeing the world, with special attention to protecting animals and Gorō. This transformation requires her to revert to her animal form and erases all her memories.

She stands 159 cm tall. Her body measurements are B:83/W:59/H:83 in the first season and B:84/W:59/H:85 in the second. She enjoys sewing, favors dark blue, and in her past life as a snake, preferred to eat frogs.