Shirayuki Mitsumine, mother of Hakuya and Mashiro, possesses a delicate frame and youthful features that frequently cause others to confuse her for a child. Her attire centers on a traditional kimono adorned with a belt showcasing a whimsical cat-head motif. Her name derives from the Japanese terms for “white” (白) and “snow” (雪), paired with the surname “Mitsumine” (三峰), meaning “three peaks.”

Eternally prone to distraction—especially by sweets—she habitually unveils consequential truths with casual nonchalance, a trait pivotal to the story when she accidentally exposes the Mitsumine family’s non-human nature. This revelation reshapes her children’s perception of their lineage and bonds. Her childlike demeanor is further highlighted during a festival arc, where she dons a school uniform and mingles undetected among students.

As part of the Mitsumine clan, she belongs to an enigmatic supernatural lineage, though her specific origins remain undefined. Her narrative role focuses on interactions with her children during their transition into the Yonomori household, where her offhand disclosures repeatedly trigger pivotal plot turns. Despite minimal direct involvement, her actions indirectly steer the evolving dynamics between Hakuya, Mashiro, and Kobeni, particularly concerning supernatural ties linked to their engagement and shared past.