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Character:

Ui is Yui's younger sister, who begins the story as a third-year junior high school student, but later enters the same school as her older sister in high school the following year. Unlike her older sister, Ui is mature, smart, responsible and handles household chores well, though she still shares a strong relationship with Yui. Despite being a year younger than Yui, she is nearly identical to her with her hair down and is even once able to fool the club. She has an extreme talent for playing the guitar, and became capable of playing with the rest of the light music club band after only a few days of practice.

Source from Wikipeida