Duan Yu is a prince who has run away from home more than once and now stands at a major turning point in his life. When he meets the most beautiful woman he has ever seen, he boldly calls her 'Fairy Sister'. Adapted from Jin Yong's novel Demi-Gods and Semi-Devils, this ONA retells the well-known tale while adding a new story of its own, mixing action, adventure and romance with a cast of many faces and tangled feelings.