The Eternal Love is set in the fictional Dongyue country where the princes fight for the throne. Due to some mystical force, Qu Tan Er develops two different personalities: she occasionally switches from gentle and reserved to uncivilized and bold. She is being offered to the eight prince Mo Lian Cheng for marriage, but Lian Cheng is suspicious of Tan Er's relationship with the crown prince for whom she once tried to commit suicide. Nonetheless, Tan Er slowly manages to gain his trust with her bold and bubbly personality and the two end up falling deeply in love. However, her other gentle personality is still yearning for the crown prince and wishes to help him become king…