Panic Palette Portable

Walking home from work late one night, Itou Aki meets a man on the beach who resembles an oil magnate from a historical novel. Before she can ask his name, he marks her with something called the Contract Mark. He explains he is a prince from the dimensional world of Meldicia, and unless the contract is dissolved, Aki is obligated to become his wife. To dissolve it, she must produce a substance called Shell Aura — which requires keeping up with school by day and wandering the town at night.