"If I get you pregnant, you'll have no choice but to be my wife."
The boy who suddenly appeared before Rin is her fiance!? But his true form is that of a man-eating demon. Rin's parents passed away when she was little and she has been living with her brother ever since, caring for the family shrine. One day, she meets a transfer student, Suo Kusa. He kisses the birthmark on her neck as he exclaims "I finally found you...!"
Suo tells her that they're childhood friends and he moved back to town to see her, but she doesn't remember anything. Then she ends up witnessing his true form... that of a demon!
"It's your fate to become my wife!" he whispers as he pulls her close...