Sakiru Tonkawa attended the same high school as Yuta Hibiki as a dedicated volleyball club member. Her accidental disruption of a special dog figurine intended as Akane Shinjo’s gift for Yuta—despite Sakiru’s immediate and sincere apology—provoked Akane’s intense anger. In retaliation, Akane collaborated with Alexis Kerib to unleash the kaiju Ghoulghilas, which annihilated the school with a fireball, killing Sakiru and her entire volleyball club during the assault. Though illusion monsters restored the school overnight, Sakiru and her clubmates were erased from existence. Their classmates retained no memory of them, and a Gridman Alliance investigation revealed Sakiru’s official records falsely listed her death years earlier in an accident, with identical fates assigned to her peers. This erasure intensified Rikka Takarada’s anxieties about memory and relationship fragility. Sakiru later manifested in a dream confronting Akane alongside other kaiju victims, though potential restoration via Gridman’s Grid Fixer Beam remained unverified. Her design included a distinctive pouch resembling a death-flag charm in promotional material, while her name and visual concept drew from GoBots’ Cy-Kill—"Sakiru" phonetically echoing Cy-Kill’s Japanese name and "Tonkawa" referencing the Tonka toy company.