Due to his playfulness Gou Er accidently touched the village's hidden soul seal. In the end, a large portion of his energy got absorbed, leaving him in great danger. Afterwards Bai Shui Er left Mirror Village with the intention of seeking someone to save him.
He is later healed by Cao Yan Bing, who agreed to help Bai Shui Er after meeting her. When Gou Er wakes Bai Shui Er tells him it was Cao Yan Bing who saved him.