Ji Yun He is a powerful demon master that resides in the Demon Valley. Despite her great talent, Yun He wishes to explore the world and live freely, but a dark secret doesn’t allow her. One day, the cruel Princess Shunde sends a merman, Changyi, to the Valley. The princess has three tasks for the demon masters: she wants the demon to speak human words, grow human legs, and serve her with loyalty. Ji Yun He is entrusted with the task of making the princess’ wishes come true, along with her adoptive brother and enemy, Lin Hao Qing. As she spends time with the merman, Yun He eventually becomes close to the demon. However, one day, she has to make a difficult decision: her freedom or the demon’s freedom?