Kanzashi Sarashiki, the younger sister of Tatenashi Sarashiki, is a first-year IS Academy student who shares her sister’s striking blue hair and dark red eyes but contrasts with a petite frame, glasses, and inward-curling locks adorned with triangular hairpins. Her shy, reserved nature drives her to withdraw as a hikikomori, often cocooned under a blanket while immersed in anime and idolizing fictional heroes.

Her isolation stems from a profound inferiority complex toward Tatenashi, whose near-flawless excellence leaves Kanzashi feeling perpetually overshadowed. This tension fractured their bond until the Tag Team Tournament and Golem III attack forced them together. Witnessing Tatenashi’s self-sacrifice and receiving unwavering support from Ichika Orimura, Kanzashi confronted her fears, mending their relationship and sparking personal growth.

As Japan’s representative candidate, Kanzashi wields sharp technical and strategic prowess, excelling in long-range combat and support roles. Initially denied a personal IS due to the prioritization of Ichika’s Byakushiki, her simmering resentment toward him faded when she ingeniously modified an academy-provided Uchigane into the customized Uchigane Nishiki, showcasing her technical brilliance.

Her dynamic with Ichika shifted from hostility to affection as he supported her during the Uchigane Nishiki’s development and tournament trials. A temporary rift emerged when she misread his kindness as mere obligation to Tatenashi, but their shared trials during the Golem III crisis and his genuine compassion dissolved her doubts. She later confessed her feelings, though Ichika initially misinterpreted her sincerity.

Subtly adopting mannerisms from Ichika’s peers, Kanzashi now playfully chides him for obliviousness, albeit with less assertiveness. Occasional cunning flashes through—like orchestrating embarrassing scenarios during events such as the Live Cosplay Changing Race—hinting at Tatenashi’s latent mischievousness beneath her timid exterior.

Through seasonal escapades in narratives like the "Long Vacation Edition" OVA, Kanzashi engages in summer festivals and poolside gatherings, reflecting her gradual social integration. Her journey from isolation to self-acceptance and familial reconciliation underscores her evolving role within the series’ ensemble, anchoring themes of resilience and connection.