Even If You Slit My Mouth

口が裂けても君には

Miroku is a slit-mouthed yokai whose powers have faded as fewer people believe in the supernatural. To keep herself alive, she enters an arranged marriage with Koichi Sano, son of a human family tasked with aiding spirits. During a trial period living together, Miroku must succeed in frightening Koichi; if she fails, she will be bound to become his wife in earnest to survive.