Shiika Anmoto, alias Fuyuhotaru or Yuki, transitions from Ishu to Hishu after awakening from a comatose Fallen state. As host to the First-Class Special Hishu-Type Mushi Fuyuhotaru, she wields destructive abilities: snowflakes that disintegrate matter on contact, lethal snowstorms targeting Mushi, high-speed tackles, and atmospheric pressure assaults. Imprisoned in the GARDEN facility following her Mushi’s temporary death, she becomes the first to escape the Fallen condition by reclaiming her Mushi and memories. Adopting the moniker "Snow Fly," she joins the resistance group Mushibane, driven by a yearning to belong.

Her appearance features short green hair, dark shimmering eyes, and pale skin, shaped by childhood habits like mimicking her sister’s long hair and cherishing a white scarf from her father. Selective amnesia erases her Fallen-era memories but preserves those of her family, spurring her quest to find them despite their unexplained disappearance. Her dynamic with Daisuke Kusuriya—who initially killed her Mushi—shifts from hostility to reluctant trust, culminating in her entrusting him with her dream of forging meaningful bonds beyond her weaponized existence.

Sheltered by resistance leader Rina Tachibana, Shiika navigates alliances within Mushibane while avoiding recapture. Her story contrasts innate gentleness with the chaos of her powers, framing a struggle to redefine her identity and seek redemption amidst forces seeking to control her.