Saki Tsukui is a middle school student transported to a fantasy world alongside four other girls the day before their graduation ceremony. Her past involves dance, where a dance team's betrayal left her struggling to trust others. This fuels a persistent fear of collaborative dance. Despite her love for dance, the betrayal caused isolation and a longing for companionship to share her passion, contributing to underlying sadness when separated from it.

Personality-wise, she initially appears aloof and reserved, easily misinterpreted as cold or rude. This stems more from communication difficulties than intentional hostility. Beneath this exterior, she possesses a caring and sweet nature. She remains quiet, rarely challenges others' assumptions about her, and prefers expressing herself through actions rather than words. Her journey requires confronting deep-seated trust issues and overcoming reluctance to form meaningful connections.

Her appearance features distinctive light lavender hair and matching eyes. She is notably short in stature and demonstrates strong dancing capabilities. Purple serves as her signature color, consistently incorporated into her design and attire throughout official media.

Her development revolves around relearning trust through the necessity of collaboration in the fantasy world. A crisis demands the five girls synchronize their hearts and movements through dance to prevent disaster. This shared mission forces her engagement with the group, gradually breaking down her emotional barriers. While the core film depicts her progression from isolation to cooperation, subsequent official crowdfunded novellas explore further aspects of her interpersonal growth beyond the original narrative.