From Midnight Scans:
Kyouko has always been alone. Her parents are always at work and she has no friends around her. One day, she found Lucifer who claims to be the Prince of the Underworld in a garden. After being rescued by Kyouko, Lucifer has decided to stake his claim on Kyouko as his wife. But why is Ishii-kun, the guy whom Kyouko confessed to suddenly wants Kyouko for himself?!