Yui Takagi, a high school student, is Atsuko Takagi's younger sister. She recently relocated to a new town with her sister and father, where Atsuko works as a teacher. Yui openly dislikes her new environment, vocalizing complaints about the town, her living situation, and the neighbors, reflecting her straightforward and honest personality.

Physically, Yui possesses blonde hair often styled in odango or twin tails, pink eyes, and a slim 152 cm frame with a 71-51-75 cm figure. Her appearance fluctuates across depictions, ranging from a teenager to possessing extremely youthful features. She wears a school uniform comprising a miniskirt, thigh-high stockings, and accessories like hair ribbons.

Within her family, Yui displays loyalty and protectiveness towards Atsuko. Both sisters engage in mutual secrecy: Yui conceals her father's abuse, while Atsuko hides blackmail from a student, both believing this shields the other and preserves family unity.

Yui develops romantic feelings for Asuma, the boy next door in her class, forming one of her few positive connections. However, she becomes ensnared in systematic community exploitation, experiencing confinement and mistreatment that mirrors the broader victimization affecting both sisters.

Her narrative emphasizes the contrast between her initial vocal resentment of the town and its inhabitants and her gradual victimization. Her commitment to protecting Atsuko compels her to endure the abuse without disclosing it to her sister.