Rimi Ushigome, a third-year Hanasakigawa Girls' High student and bassist of Poppin'Party, battles shyness and stage fright rooted in her reserved nature and comparisons to her older sister Yuri, Glitter*Green’s vocalist. Her pink bass—a hand-me-down from Yuri—serves as both a musical catalyst and a bond to her sister, who inspired her musical path after a childhood performance. Hailing from the Kansai region, her dialect slips through when nervous, a quirk she self-consciously masks.

At her high school entrance ceremony, Kasumi Toyama’s spirited introduction caught her attention, though anxiety led her to initially reject Poppin'Party. A turning point arrived when Kasumi’s spontaneous Live House SPACE performance covered for Glitter*Green’s delay, galvanizing Rimi to confront her fears and join the band. Over time, performances and songwriting—including a chocolate cornet-themed collaboration with Yuri, referencing Yamabuki Bakery treats—bolstered her confidence. She maintains daily updates to Yuri after her sister’s overseas studies, underscoring their closeness.

Academically diligent, she enrolls in second-year cram school for university exams. Her hobbies span horror media, gaming, and reading, though she avoids haunted houses and detests mint chocolate. Standing 150 cm, she often voices a wish to grow taller, a recurring theme in conversations. She addresses bandmates with "-chan" and runs a blog reviewing sweets, an idea proposed by friend Himari.

Alternate portrayals include her role in the "Girl’s Blossom Project" April Fools’ dating sim as Himari’s classmate and Kaoru’s devoted fan, frequenting drama club rehearsals. A cheeky ninja persona emerges in another storyline, where she sells rice at school and demands Poppin'Party become "Japan’s greatest" before joining—contrasting her usual timidity with unexpected assertiveness.