A homunculus, an artificial human and living weapon, was created by Hibiki. This creation was intended for Yutsuko, who sought to replace her deceased child with a homunculus but only managed to create unstable blob-like creatures that vanished after three days.
After considerable effort, Hibiki and Shirotsuki succeeded in creating a homunculus. Initially quite bratty and mischievous, she eventually formed a warm relationship with Hibiki. However, Shiraasan remained an incomplete being, putting her life at risk.
Her existence was later stabilized, and she became something akin to a sister-daughter to Hibiki. Living with Hibiki, she often gets involved in her mishaps, along with Ahito.
As a homunculus, Shiraasan possesses the ability to materialize guns and other weapons, a power that manifests when her pupils narrow. However, as a magical being, overusing her powers can cause her to disappear.
