Euphrosyne Studion, born into nobility, perished in a sudden accident. Her father resurrected her as a zombie using magic, embedding a vital "stone of life" within her body to sustain her existence and power. Following this resurrection, she and her maid, Alma V., entered a prolonged dormant state. Roughly a century later, members of an Occult Research Club discovered their mummified forms in a university data warehouse. Club member Sayaka Kamoshida stole Euphrosyne's stone of life, triggering her awakening. Deprived of the stone, Euphrosyne survived on her remaining limited energy, forcing her to conserve it through restrained actions despite possessing significant physical capabilities.

Physically, she resembles a young girl with blonde hair tied in a ponytail and red eyes. Her undead nature grants her superhuman strength, high vitality, resilience to injury, and the ability to reattach her head if severed. She is also a skilled martial artist. Her primary motivation upon awakening was retrieving the stolen stone to ensure her survival.

Alongside Alma, she pursued the Occult Research Club members across the university campus to reclaim the stone, leading to violent confrontations and several deaths among the club. The stone was passed to Professor Shuichiro Takanashi, who implanted it into his sister Mako, transforming her into an immortal. Euphrosyne battled Mako, who initially held the advantage due to Euphrosyne's diminished energy. Euphrosyne ultimately defeated Mako by trapping her under a falling church bell and crushing her head, retrieving the stone from Mako's body.

Her characterization includes moments of absent-mindedness and a casual demeanor, contrasting with her lethal abilities. She displays fierce determination when protecting her existence or confronting those possessing her stone.