Shizuru Shirakawa, the compassionate older sister of Hotaru Shirakawa, balances university life with a nurturing presence. As a literature student advancing from her third to fourth year, she mentors Shougo Kagaya, her junior, while maintaining a close bond with Koyomi Kirishima, her high school best friend. Their shared passion for professional wrestling extends to Shizuru coaching others, including Shougo and Koyomi, blending physical discipline with camaraderie.

Her protective instincts shine in guiding Hotaru through personal challenges, particularly those involving Ken Inami, and she actively supports peers like Isshu Sagisawa, urging him to resolve Inori Misasagi’s emotional conflicts. Renowned for her dessert-making skills, Shizuru’s creations earn adoration from Hotaru, blending sweetness with her quiet reliability.

Deputy manager of the Narazuya cafe in *Memories Off: Sorekara*, she anchors key events, offering solace after the tragic accident involving Kanata Kurosu and Cubic Cafe’s manager. Despite her calming influence, Shizuru’s notoriously reckless driving contrasts humorously with her composed demeanor.

Her name, "static stream" (静流), mirrors her steady temperament, while "Shirakawa" (白河)—"white river"—symbolizes her unwavering support as a sister, mentor, and community pillar. These traits persist across interconnected stories, cementing her role as a stabilizing force without drastic personal evolution.