From a young age, Chihiro Furuya, obsessed with zombies, dreamed of an undead girlfriend. His passion for the macabre proves useful when his cat Baabu is hit by a car, and Chihiro attempts to brew a revival elixir to resurrect him. While experimenting, he encounters Rea Sanka, a wealthy girl who daily screams into an ancient well about her oppressive existence. After forming a connection with her, Rea persuades Chihiro to persist in rescuing Baabu. With the aid of poisonous hydrangea blossoms from Rea's family garden, he eventually succeeds.
Unaware that the potion has worked and wishing to free herself from her burdens, Rea consumes the resurrection brew, mistakenly believing it will kill her. The concoction does not cause death but leaves lingering effects; when she later dies in a fatal mishap, she is reborn as a zombie. Supported by Chihiro, Rea learns to navigate her new undead existence.
For a boy longing for a zombie partner, this scenario seems like a fantasy realized. Yet in Sankarea, Chihiro"s life grows stranger as he confronts Rea"s bizarre new desires and the unexpected fallout of her transformation.