Hanatsukihime

When Lys was born, her heart did not beat at all. To save her, her mother made a contract with a devil: Lys can borrow his heart until the day she turns sixteen, but after that, he will eat her body. Together with her companion, Siva, someone whom she met by chance in the desert at night, she travels around as a dancer girl to find the devil who sealed her fate. One day, while they were traveling, they suddenly meet an egoistic prince and a ring spirit...