Xiaohei (Wang Heng) and Xiaobai (Yan Liang) are an ordinary team of Black Guard & White Guard (the soul collector) in the underworld. Xiaobai, who has shocking secrets and a huge amount of hidden power, has been targeted by all the beings from three realms. As the brother of Xiaobai, Xiaohei cannot but become the most ferocious fighter to protect his sister and the safety of heaven and earth. Xiaohei and Xiaobai, who are in jeopardy, embark together on a journey into the unforeseeable future.