Rinko Shirokane is the keyboardist for the band Roselia, initially paralyzed by extreme shyness and social anxiety, particularly terrified of live performances. Despite her withdrawn and pessimistic nature, she demonstrates fierce determination for pursuits she values. A former student council president at Hanasakigawa Girls' High School, she now studies piano as a first-year in the Faculty of Arts Music Department at Yotsuba Women's University. Her interests extend to online gaming, solving crossword puzzles, and reading. She favors warm milk while actively avoiding celery.

Her close friendship with Ako Udagawa began through online gaming, marked by moments like Rinko's shyness when Ako hugs her or gently holds her hand. Within Roselia, Rinko takes responsibility as the primary costume designer, crafting the band's outfits with her sewing skills—a role that sometimes leads to embarrassment, such as when adjusting clothing measurements around another member's waist.

Rinko's character development centers on overcoming intense stage fright. Through persistent participation in Roselia's activities, she gradually builds confidence, transitioning from anxiety to dedicated involvement. Her keyboard playing remains an integral component of the band's musical identity, reflecting her resilience.