The tale begins during the arduous pilgrimage of the monk Tang Sanzang and his three disciples as they travel toward the Western Paradise to retrieve sacred Buddhist scriptures. Friction had always existed between the temperamental Sun Wukong and his master, but it reached a breaking point when Wukong used lethal force against a group of bloodthirsty bandits. Tang Sanzang, bound by the Buddhist vow of non-violence and mercy, was horrified by the carnage. Despite Wukong’s insistence that he was merely protecting the group, the monk recited the Band-tightening Spell, causing the golden circlet on Wukong's head to constrict painfully. Driven away in disgrace, the Great Sage Equal to Heaven departed for the South Sea to seek solace from the Bodhisattva Guan Yin.
While the real Sun Wukong was away, a mysterious figure descended upon the remaining pilgrims. This figure looked, spoke, and acted exactly like Sun Wukong. He carried a staff identical to the Ruyi Jingu Bang and wore the same golden mail and phoenix-feather cap. However, this was not the repentant disciple returning to apologize. It was the Six-Eared Macaque, an ancient and cunning being who possessed the unique ability to hear everything in the universe, past and future, and to mimic anything he observed. The impostor struck Tang Sanzang unconscious, seized the travel luggage containing the emperor's transit passes and the precious alms bowl, and fled to the Flower and Fruit Mountain. There, he established a false court, even manifesting fake versions of Pigsy and Sandy to accompany him on a mock journey to claim the scriptures for himself.
When the true Sun Wukong learned of the robbery, he flew into a primal rage. He confronted the impostor at the Water Curtain Cave, and the two began a duel that shook the very foundations of the earth. Their powers were perfectly matched. Every strike of the real Ruyi Jingu Bang was met with an equal blow from the impostor's weapon. They leapt through the clouds, their combat spanning thousands of miles in a matter of seconds. Realizing that brute force alone would not settle the dispute, they traveled together to the South Sea, demanding that the Bodhisattva Guan Yin identify the fraud. However, even the Bodhisattva, with her immense wisdom and divine sight, could not tell them apart. Both monkeys possessed the same memories, the same techniques, and even the same scent. The golden circlets on their heads were identical, and both seemed to suffer equally when she recited the restraining spell.
Frustrated, the two monkeys ascended to the Heavenly Court to seek a judgment from the Jade Emperor. The celestial bureaucracy was thrown into chaos as two Great Sages fought in the halls of the Lingxiao Palace. The Jade Emperor ordered the use of the Terrestrial Mirror, a powerful artifact capable of revealing the true forms of demons and monsters. Yet, when the mirror's light fell upon the two monkeys, it reflected two identical Great Sages. The Six-Eared Macaque’s mimicry was so absolute that it transcended the physical realm, fooling even the most potent of heavenly treasures. The Jade Emperor, fearing further disruption to the celestial order, could only turn them away, leaving the two combatants to continue their ferocious struggle across the sky.
Descending into the depths of the Earth, the pair sought the judgment of the Ten Kings of Hell. In the gloomy halls of the Underworld, they appealed to Ksitigarbha Bodhisattva. Ksitigarbha summoned his divine mount, the beast Diting, which possessed the ability to distinguish the truth of all things in the cosmos by listening to the vibrations of the soul. Diting crouched and listened, its ears twitching as it perceived the essence of the two combatants. The creature looked up with wide, fearful eyes and whispered to its master that it knew which was the real Wukong. However, Diting warned Ksitigarbha that the impostor was as powerful as the original, and if they revealed the truth there, the resulting battle would destroy the Underworld entirely. Following the beast's advice, the Bodhisattva remained silent and suggested they seek the ultimate wisdom of the Buddha at the Thunder Monastery on Vulture Peak.