Yui Hirasawa
Ui hugging Yui Yui is the older sister of Ui Hirasawa, although Ui acts more like the "older sister" of Yui, as she is more responsible and mature enough to take care of her older sister. Yui is quite happy to have Ui as a sister and loves her very much. This is proven when she decides to make a meal for Ui when she got sick taking care of her despite her lack of cooking skills compared to Ui.  Yui even dedicates one of the very first songs that she writes to Ui.
Jun Suzuki
Ui and jun Jun and Ui had been friends since primary school. They also went to the same junior high school and spend a lot of time together. In their first year, Ui tried to persuade Jun to join the Light Music Club, but Jun declined and instead joined the Jazz Club. In their third year, after the senior members of the Light Music Club had left for university, Jun and Ui together finally joined Azusa in building the new Light Music Club (Wakaba Girls) and recruiting other students from their school to get involved.
Azusa Nakano
Ui and azusa Azusa and Ui also had been good friends since their first year of high school. At that time, Ui introduced Azusa to the Light Music Club, accompanying her to their live performance at the freshman reception and persuading her to join the club.

After that event, they became good friends. When Azusa worried about new club members for the new Light Music Club, Ui and Jun gave her confidence by joining the club and together trying to persuade other students to get involved.