The Bull Demon King, also known as Great Sage Who Pacifies Heaven, is the husband of Princess Iron Fan and Princess Jade Face, and the father of Red Boy. He is also the sworn brother of Sun Wukong, from the time when Sun Wukong ruled as the Handsome Monkey King. Sun Wukong calls him "Big Brother." After Sun Wukong was imprisoned, the Bull Demon King moved to Flaming Mountains, where he married Princess Iron Fan and fathered Red Boy. Later, he married Princess Jade Face and lived in her Cloud-Piercing Cave.

First Request for the Banana Leaf Fan

When Tang Sanzang and his disciples passed through Flaming Mountains, they were blocked by raging flames. Sun Wukong learned that Princess Iron Fan's Banana Leaf Fan could extinguish the fire, so he went to Banana Leaf Cave on Green Cloud Mountain to borrow it. However, because Sun Wukong had previously caused her to be separated from her son Red Boy, Princess Iron Fan refused his request. After a heated argument, she used the Banana Leaf Fan to blow Sun Wukong thousands of miles away.

Second Request for the Banana Leaf Fan

Not long after, Sun Wukong returned to Banana Leaf Cave to borrow the fan again. Another argument ensued, and they started fighting. Knowing she couldn't defeat him, Princess Iron Fan once again tried to blow Sun Wukong away with the fan. This time, Sun Wukong was prepared and used a magical Wind-Stopping Pearl given to him by Lingji Bodhisattva to counter the fan's power. Seeing that the fan was ineffective, Princess Iron Fan fled back into the cave. Sun Wukong transformed into a tiny insect and hid in her tea. When she drank the tea, he entered her stomach and caused her great pain. Unable to bear it, she begged for mercy and agreed to lend him the fan. However, when Sun Wukong tried to use the fan, he discovered it was a fake that made the fire burn even more fiercely.

Third Request for the Banana Leaf Fan

Desperate, Sun Wukong went to the Cloud-Piercing Cave to seek the Bull Demon King's help. His urgency angered Princess Jade Face, who complained to her husband. Already harboring a grudge against Sun Wukong over the Red Boy incident, the Bull Demon King was further incensed by Sun Wukong's behavior. Though he initially didn't want to fight his sworn brother, he changed his mind when he learned about the request for the Banana Leaf Fan, suspecting that Sun Wukong had also bullied Princess Iron Fan. Enraged, he took up his weapon and fought Sun Wukong.

After battling for dozens of rounds, the Dragon King of Clear Wave Pond (Bi Bo Tan) invited the Bull Demon King to a banquet. The Bull Demon King warned Sun Wukong to stop causing trouble and left for the banquet. Seizing the opportunity, Sun Wukong transformed into the Bull Demon King, rode his mount to Banana Leaf Cave, and tricked Princess Iron Fan into giving him the real Banana Leaf Fan and the spell to use it.

When the Bull Demon King returned and found his mount missing, he immediately realized that Sun Wukong had tricked Princess Iron Fan. He rushed to Banana Leaf Cave, only to find that Sun Wukong had already succeeded. Using Sun Wukong's own tactics, he transformed into Zhu Bajie to deceive Sun Wukong and retrieve the fan. Sun Wukong, proud and showing off to Zhu Bajie, realized he had been tricked and angrily resumed the fight with the Bull Demon King.

The Epic Battle

Zhu Bajie joined the fight, and the Bull Demon King, unable to withstand their combined strength, retreated to the Cloud-Piercing Cave. Sun Wukong and Zhu Bajie pursued him, forcing the Bull Demon King to turn and continue the battle. Princess Jade Face led her minions into the fray but was no match for Sun Wukong and Zhu Bajie. The Bull Demon King transformed into a swan to escape, but Sun Wukong followed. Princess Jade Face, unable to flee in time, was killed by Zhu Bajie in the Cloud-Piercing Cave.

The Bull Demon King reverted to his true form and continued to fight Sun Wukong. Their battle lasted for days and nights, drawing the attention of the Heavenly Court. Exhausted, the Bull Demon King returned to Banana Leaf Cave, while Sun Wukong sought reinforcements. Eventually, the Bull Demon King was defeated by Nezha and Li Jing, father and son deities. He handed over the Banana Leaf Fan to Sun Wukong, allowing the monk and his disciples to continue their westward journey.

From that point on, the Bull Demon King and Sun Wukong, once sworn brothers, became mortal enemies.