In the third year of the apocalypse, Lin Yue, who has no supernatural abilities, awakens the Animal Girl Transformation System when pushed to the brink of despair. His ordinary dog, Xiaoguo, transforms into a combat girl and slashes a zombie with one strike. The two level up by collecting crystal cores and deepening their bond, fighting their way from F-rank to S-rank. As the authorities try to recruit them and villains attempt to seize their power, a mastermind doctor controls a zombie army to besiege their base. In the end, Lin Yue and Xiaoguo defeat the doctor and avert the apocalyptic crisis.