One fateful night, atop a towering mountain, a monkey emerges from a stone, inadvertently disrupting the Jade Emperor's peace. Just as the Emperor, portrayed by Hoon Lee, prepares to eliminate the newborn cub, a wise Buddha—voiced by BD Wong—steps in, advising the Emperor to allow the little one to discover his true purpose.
The Jade Emperor, as the celestial sovereign, watches over Heaven, while Buddha serves as the luminous guide of the Universe. In his quest for belonging, the monkey ventures into the wild, joining a band of other monkeys; however, his mischievous tendencies hinder his ability to fit in. An unfortunate incident leads to a dreaded demon emerging from his lair, snatching one of the troop's young. This tragedy causes his exile, compelling the monkey to embark on a journey of self-improvement. He rigorously trains to confront the demon and reclaim his place among the others.
Years later, confident in his newfound skills, the monkey challenges the demon, but to his dismay, his training is insufficient, resulting in yet another cub being seized. Determined to retrieve a weapon worthy of a god, he plunges into the underwater domain of the Dragon King, played by Bowen Yang, who revels in his power as he plans to use a potent, glowing column to wipe out humanity. Drawing courage from within, the monkey communicates with this mystical column, transforming it into a staff, and manages to escape with his formidable new weapon.
Empowered by his staff, the monkey returns to battle the demon, ultimately defeating the beast and rescuing the cub. In a bold proclamation, he crowns himself King of the Monkeys, with Jimmy O. Yang lending his voice to this spirited character. However, the troop's wise Elder Monkey, voiced by James Sie, warns him that such a staff is meant for the gods alone. Driven by ambition, the newly crowned Monkey King sets forth to eliminate 100 demons, thereby earning his rightful place among the deities in Heaven.
His journey takes him far and wide, as he successfully defeats 99 demons, revealing a harrowing battle against the Red Girl in a village. With the encouragement of a brave girl named Lin, portrayed by Jolie Hoang-Rappaport, the Monkey King triumphs over her threat, and Lin offers her allegiance as his assistant. Yet, despite this hard-won victory, the celestial beings fail to acknowledge the Monkey King, leaving him in a state of confusion and frustration.
In the midst of a joyous celebration, the Dragon King returns from the depths of the sea to reclaim the staff he desires. As their titanic battle unfolds, it becomes apparent that the Dragon King's connection to water limits his time on land. Following a struggle, the Monkey King maintains possession of his staff while Lin, underestimating the true nature of her intentions, secretly serves the Dragon King in a bid to rescue her village from disaster.
As the Monkey King learns from the staff that true immortality is key to his ascension, his partnership with Lin grows complicated. The duo discovers that to erase his name from the Scroll of Life and Death, they must access the Archive of Souls in Hell, guarded by King Yama, played by Andrew Kishino, the formidable ruler of the underworld. Their daring incursion leads to an intense confrontation, but with Lin’s clever assistance, they manage to strike his name from the scroll, albeit achieving only agelessness rather than immortality.
Through cunning, the Monkey King discovers that true immortality can be obtained by consuming a divine peach from the Orchard of Everlasting Life. However, he soon falls into a trap set by the Dragon King, who attempts to mislead him to an illusory tree. When the truth surfaces, the Monkey King learns about Wangmu, the Divine Queen Mother, voiced by Jodi Long, who concocts a celestial elixir for the divine. Partnering with Lin, he breaches the Jade Palace's pharmacy in a desperate attempt to create the elixir. Despite being caught in the act, the Monkey King manages to ingest the potion, finally achieving full immortality.
As they navigate their intricate relationship, Lin has multiple opportunities to betray the Monkey King; however, she ultimately chooses to stand by him, revealing the depth of their bond. Even amidst the ongoing chaos, the Monkey King demonstrates his affection for her, which only complicates their adventures further. After they escape the Heavens, Lin shares her dream of making a difference in the world, endeavoring to encourage the Monkey King to adopt a similar mindset.
When the Monkey King remains obstinate and self-centered, Lin outsmarts him, delivering the staff to the Dragon King, who immediately betrays their agreement, threatening to unleash a catastrophic storm upon the world. With Lin recognizing the gravity of her mistake, she cleverly tricks the Dragon King into attacking the Monkey King with lightning, thus granting him the strength he needs to conquer his foes. Yet, in a moment of intoxication with power, the Monkey King directs his rage towards the heavens themselves.
As the threat escalates, Buddha considers intervention, yet Lin advocates for the Monkey King, believing in his capacity for goodness. Acting as Buddha’s voice, she challenges the Monkey King: he must leap off of Buddha's hand to claim dominion over Heaven, or face a period of penance for failure. Ultimately, he falters, unable to escape the cosmic weight of the Universe, leading to his imprisonment beneath a mountain.
Before the final seals are placed upon his prison, Lin bids farewell, while the Monkey King acknowledges her impact on his life for the first time. After an agonizing 500 years of solitude, a monk, a pig, and a river spirit release him on Buddha's orders, inviting him to join their mystical journey to the West—a proposition he gladly accepts, full of hope and renewed purpose.
