In the city of Donghai, whose lower-class residents are suffering from a major water shortage, Li Yunxiang, an underground motorbike racer, works as a smuggler against the wishes of his father, while secretly providing his fellow residents with water by causing breaches in water plants. One night, Ao Bing, son of Ao Guang, leader of the De Clan, the syndicate ruling the city, arrogantly chases after Yunxiang and his sister Kasha to claim his bike. Left wounded and with Kasha injured, Yunxiang’s inner fury unleashes a mysterious power that burns Ao Bing’s arm, forcing them to flee.
At a hospital, where a woman he met at one of his races, Su Junzhu, works, Yunxiang awakens to discover his wounds healed and, following the previous night’s incident, Kasha having lost her right leg. When Ao Guang appears and personally apologizes to Yunxiang and his brother Jinxuang for his son’s actions, even returning his bike and offering a generous amount of money, an embittered Yunxiang rejects it. Recognizing his power, Ao Guang sends his forces to kill Yunxiang, running Jinxuang off the road in the process, while Yunxiang defeats the assassins with his powers.
Yunxiang is rescued by a mysterious masked man, who reveals to him that he is the reincarnation of Nezha. Confused, Yunxiang leaves. Meanwhile, Ao Guang reveals to his son of Yunxiang’s true identity and that Ao Bing’s past life was nearly killed by Nezha before a steel spine was built to help him survive, spurring Ao Bing to swear his revenge against Nezha. Ao Guang then visits the masked man and offers him a sum of money to kill Yunxiang, which he refuses.
Back at the hospital, seeing his new abilities difficult to control, Yunxiang returns to the masked man, who, in exchange for a brand-new bike, trains him to control his powers; as he learns to master his skills, he creates special armor to control the flames and builds Kasha a prosthesis. During a practice fight, Yunxiang discovers the masked man’s identity as the Six-Eared Macaque, while learning more about Nezha’s primordial spirit within him. While at the hospital, Ao Guang’s right-hand, a frog demon, attacks, but is swiftly defeated by Yunxiang.
However, Liang, one of Yunxiang’s former coworkers who envies his newfound power is tipped off by Ao Guang to sabotage his armor. He kills Yunxiang’s friend Six and targets Kasha to cover it up, who escapes before the hospital is bombed by more De Clan assassins. Yunxiang dispatches them before being attacked by a one-armed warrioress, Rosy Cloud, although he forces her to flee. Upon returning to the hospital, he finds his father wounded in the aftermath, who apologizes to Yunxiang before succumbing to his wounds. Aggrieved and angered, Yunxiang departs for the De Clan base.
At the De family mansion, the Macaque arrives for a personal discussion with Ao Guang, discovering creatures enslaved by him that have drawn all the city’s water before Yunxiang arrives, killing his forces before battling Ao Bing; he transforms into his dragon form, but Yunxiang defeats him by ripping off his metallic spine. Rosy then attempts to strike Yunxiang down, but the Macaque intervenes and restrains her, revealing her as the disciple of the Demoness Shiji. Rosy bitterly explains she seeks revenge against Nezha for him killing a dear friend of hers as an act of amusement. Yunxiang then discovers Nezha’s past, where, after killing Ao Bing’s previous life, the Dragon King of the East Sea demanded an apology, lest he drowned the entire city. Arrogantly refusing, Nezha killed himself. Disillusioned by this revelation, Yunxiang lets Rosy go.
As Yunxiang lays in shock, the Macaque reveals that he himself is Sun Wukong, the Monkey King. He reveals that Ao Guang’s undersea palace holds the city’s water, as well as the river dragons living within it being restrained to create an item that he needs to grow in power, a Dragon Pearl. Discouraged, Yunxiang then mourns his father at his grave, but inspiration from Su and Kasha invigorates him, and he heads toward Ao Guang’s palace.
Upon infiltrating the palace, Yunxiang attempts to free the lion-like creatures under Ao Guang’s enslavement, but Ao Guang intervenes, while having kidnapped Su to distract him. Though he struggles, Yunxiang kills Rosy and overpowers Ao Guang, though he returns in his dragon form, swallowing the Dragon Pearl to force the river dragons to wash the city away in a massive tsunami. Yunxiang attempts to stop the dragons by using the Sky Ribbon, but it breaks, allowing the dragons to scatter. Ao Guang attempts to finish Yunxiang off, but Yunxiang harnesses Nezha’s power to kill him, at the cost of his own life.
The dying Yunxiang pleads with Nezha to save the city, and the primordial spirit revives him, unifying them as they use the Sky Ribbon to redirect the dragons from the city, stopping the tsunami. Afterward, Yunxiang settles back into his life, accepting his role as a hero.
