Since childhood, Chihiro Furuya has harbored an obsession with zombies, longing for one as a companion. After his cat Baabu is struck by a car, Chihiro attempts to craft a resurrection potion to restore it. While conducting his experiments, he encounters Rea Sanka, a girl from a wealthy family who vents her frustration with her controlling home life by shouting into an abandoned well. The two grow close, and Rea supports Chihiro's efforts, which eventually yield a successful potion brewed from the toxic hydrangeas in her family's garden. Unaware of the potion's true effects, Rea drinks it hoping to end her suffering, believing it will kill her. Instead, the potion's properties combine with a tragic accident, transforming Rea into a zombie. Chihiro assists her in adapting to this new existence. Although his dream of a zombie girlfriend appears to come true, life in Sankarea becomes increasingly strange as Chihiro grapples with Rea's new urges and the unforeseen consequences of her transformation.