as humans, hai xin and xia fan got the magical energy they had always dreamed of by chance. aaa。 with the consent of the demon fairy xiya, he became a little demon fairy and protected the human world and the magic ocean with xiya. while helping xiya investigate the sea beasts that pollute the magical ocean, they met prince haida of the sea firefly castle and other demon immortals. everyone encountered many difficulties in the journey to seek the truth, but everyone united and worked together to overcome many difficulties.