"If I impregnate you, then you'll have no choice but to marry me."
Rin thought she had just met her fiance, but he's actually a man-eating demon. After her parents' death, she's been living with her brother and taking care of their family shrine. However, when she meets transfer student Suo Kusa, he claims to be a childhood friend she doesn't remember. But when she witnesses his demon form, he declares that she is fated to be his wife.