The Moon Fox clan determines status by the number of tails. Ten-year-old Xiaobai has only one tail and is publicly judged by the clan as a "useless tail", being banished from Yueze. In desperation, he accidentally awakens the Nine-Pearl Key, learning that his long-lost mother Bai Yue is still sealed behind nine profound ice gates. To save his mother, Xiaobai follows the broken-tailed guardian Bai Wang onto the snowfield, and gradually discovers that clan leader Xuanzhua's nine tails come from plunder, while his own most inferior single tail turns out to be the only key to unlock the truth. Facing Xuanzhua, who also walked up from a single tail, Xiaobai chooses not to seize or snatch, growing in his own way.