Ever since childhood, zombie-obsessed Chihiro Furuya has desired an undead girlfriend. His fascination with all things zombie soon proves useful when his cat, Baabu, is run over, prompting Chihiro to attempt brewing a resurrection potion to bring the pet back to life. During this endeavor, he notices a wealthy girl named Rea Sanka yelling into an old well daily about her oppressive life. After meeting and bonding with her, Chihiro is convinced by Rea to persevere in saving Baabu. Eventually, he succeeds with the help of poisonous hydrangea flowers from Rea's family garden. Unaware of the potion's success and seeking to escape the burdens of her life, Rea drinks the resurrection potion, mistakenly believing it will kill her. Although it does not kill her, the effects linger, and her death from a fatal accident causes her to be reborn as a zombie. With Chihiro's help, Rea strives to adjust to her new—albeit undead—life. For a boy wanting a zombie girlfriend, this situation would seem like a dream come true. But in Sankarea, Chihiro's life becomes stranger than usual as he deals with Rea's odd new cravings and the unforeseen consequences of her transformation.