Red Boy, also known as the Boy Sage King, is the son of the Bull Demon King and Princess Iron Fan. After three hundred years of cultivation on the Flaming Mountains, he mastered the Samadhi Fire.

Red Boy lived in the Fiery Cloud Cave in the Withered Pine Valley of Drillhead Mountain, which spanned six hundred miles. When he learned that Tang Sanzang and his disciples were passing through Drillhead Mountain, he decided to capture Tang Sanzang to eat his flesh and gain immortality. Disguising himself in a red light, he attempted to seize Tang Sanzang but was thwarted by Sun Wukong, who protected his master, leaving Red Boy with no opportunity.

Disguising as a Child to Gain Trust

Red Boy then transformed into a seven-year-old naked child, bound his hands and feet with rope, and hung himself from a pine tree, crying for help. Sun Wukong recognized the child as a Yaoguai and tried to prevent Tang Sanzang from rescuing him. However, this only angered Tang Sanzang, who insisted on saving the child. Red Boy lied, claiming he was the son of a wealthy family who had been robbed and left hanging from the tree by bandits.

Zhu Bajie freed Red Boy from the ropes. Red Boy then pretended his limbs were numb and tricked Sun Wukong into carrying him. Sun Wukong, intending to kill Red Boy, agreed. However, Red Boy saw through Sun Wukong's plan and used his powers to press a thousand pounds of weight on Sun Wukong's back, then employed a corpse-escaping technique to leave a fake body on Sun Wukong's back while he himself jumped into the air. Sun Wukong, unaware of the trick, smashed the fake body to pieces, while Red Boy seized the opportunity to create a gust of wind and kidnap Tang Sanzang.

The Samadhi Fire

Sun Wukong learned from the local keeper that Red Boy was the son of his sworn brother, the Bull Demon King. He and Zhu Bajie then went to Red Boy to claim kinship. Red Boy arranged five small carts according to the Five Elements and, barefoot and armed with a fire-tipped spear, fought against Sun Wukong. When Zhu Bajie saw that Red Boy was no match for Sun Wukong, he tried to seize the opportunity to claim credit but was thwarted when Red Boy escaped and used the Five Elements carts to unleash the Samadhi Fire, forcing Sun Wukong and Zhu Bajie to retreat.

Sun Wukong sought help from the Dragon Kings of the Four Seas, but Red Boy's Samadhi Fire burned even more fiercely when it encountered rain. Sun Wukong tried to capture Red Boy within the flames but was met with a blast of smoke from Red Boy, which stung his eyes so badly that he had to flee and dive into the water, barely escaping with his life.

Clever Boy

After his victory, Red Boy anticipated that Sun Wukong would seek reinforcements. He left his cave to keep watch and saw Zhu Bajie flying south on a cloud, deducing that he was going to ask Guanyin for help. Red Boy took a shortcut to get ahead of Zhu Bajie and, disguised as Guanyin, lured Zhu Bajie into the Fiery Cloud Cave and captured him.

Red Boy then sent six warriors to invite the Bull Demon King to feast on Tang Sanzang's flesh. Sun Wukong, learning of this, disguised himself as the Bull Demon King and accompanied the warriors back to the Fiery Cloud Cave. After a conversation, Red Boy realized that the Bull Demon King was actually Sun Wukong in disguise and tried to capture him, but Sun Wukong managed to escape.

The Five Golden Rings

Sun Wukong personally went to the Southern Sea to invite Guanyin. Using a feigned defeat strategy, he lured Red Boy to Guanyin. When Red Boy saw Guanyin remain silent, he attacked her with his spear. Guanyin flew away, leaving her lotus pedestal behind. Red Boy imitated Guanyin and sat cross-legged on the lotus pedestal, which then transformed into numerous sharp blades that pierced his legs. Suffering greatly, Red Boy tried to pull out the blades, but Guanyin turned them into bar bed hooks, making it impossible for him to remove them. In pain, Red Boy begged Guanyin for mercy, falsely claiming he wanted to convert. Guanyin retracted the barbed hooks, but Red Boy immediately turned hostile again and attacked her with his spear.

Seeing this, Guanyin took out five golden rings from her sleeve and placed them on Red Boy's head, hands, and feet. She then recited the "Golden Hoop Incantation," causing Red Boy unbearable pain. With no other choice, Red Boy finally submitted and agreed to convert. Due to Red Boy's wild and unruly nature, Guanyin instructed him to bow with each step all the way to Mount Luojia, where he became the child attendant named Shancai (Sudhana).