Hwayugi

In 2017, Son Oh-gong (Sun Wukong) and Ma-wang Bull Demon King) are in conflict with each other as they look for a true light in a dark world where evil thrives. From there, Son Oh-gong is bound to his protective role towards Seon-mi (Sanzang), the little girl he had met years ago. Having made a contract with Seon-mi 25 years ago, entitling her to seek help from Son Oh-gong whenever she calls him in exchange for letting him free, the two meet again in a fateful encounter.

Seon-mi is a young girl born with the ability to see ghosts and spirits. Her seemingly irrational behavior has isolated her from her family and peers, and her only protection is her grandmother and a small yellow umbrella with protection spells written by a Buddhist monk. One day when she walks home from school, a ghost follows her, and this is witnessed by a mysterious man in a suit and black top hat (Woo Ma-wang). The mysterious man exorcises the ghost for her, and asks her for a favor: to enter a magical house and retrieve a certain fan. She is also given specific instructions to ignore anyone she sees in there. However, the person inside the house is Son Oh-gong, the Monkey King, who was imprisoned inside by Heaven for his crimes. He blocks her path and forces her to acknowledge him, and tells her that the man outside is a great danger to her as well. Oh-gong makes her a deal: if she puts out the five candles on the table and frees him, he promises to protect her from all dangers in her life every time she calls his name. But after she agrees and releases him, Oh-gong steals the memory of his name out of her head and makes a run for it, leaving young Seon-mi stranded in the middle of nowhere.

In the present day, Seon-mi has grown up into an adult. Still armed with her little magic umbrella, she owns a real estate company that specializes in buying haunted houses, exorcising the spirits, and then flipping them for large profits. At a busy intersection, Seon-mi and Oh-gong spot each other and Seon-mi asks why he did what he did. He gives an unsatisfactory answer and Seon-mi tearfully asks aloud why she ever bothered having faith in him as a child. Meanwhile, Son Oh-gong is looking to reinstate his status as an immortal and has been doing various good deeds to earn brownie points with Heaven. He learns from a possessed doll that Sam-jang (Sanzang) has been born, and anyone who eats Sam-jang's flesh can gain immortality. He decides to figure out who it is and eat them. However, Sam-jang is none other than Seon-mi, which means that Oh-gong cannot eat her without violating the promise he made to her as a child that he would protect her.

While Oh-gong tries to figure out a way to convince Seon-mi to die for him, Soo Bo-ri goes to Woo Ma-wang and asks him for help in protecting Sam-jang. Ma-wang takes Seon-mi to a antique shop with magical wares. There an old lady (Bodhisattva Guanyin) sells him a Geumganggo, a magical bracelet that will ensure the obedience of anyone who wears it through the power of love. The original Geumganggo is worn on the head, but this version is worn on the wrist. Seon-mi gives it to Oh-gong as a gift on Christmas Eve, and has a prophetic dream about standing in a field, wearing a hanbok, and giving him a kiss.

This dream comes true when Seon-mi is dragged into a haunted painting by a malevolent spirit that kidnaps women and tries to marry them all. Oh-gong enlists the help of Pal-Kye (Zhu Bajie), a pig demon and pop artist under Ma-wang's entertainment company, to get inside the painting. Pal-gye helps him, but he and Ma-wang burn the painting instead, trapping both Seon-mi and Oh-gong inside. Seon-mi decides to follow her dream and kisses Oh-gong, thus activating the Geumganggo, though she did not realize what the Geumganggo would do. Oh-gong gives back her memory of his name and forces her out of the painting world, because he cannot leave the painting world unless she summons him from the outside. Seon-mi cuts her own hand and attracts a hoard of demons to her before calling out Oh-gong's name. Oh-gong exits the painting world and rescues her from the demons.

From then on, the main plot is focused on Seon-mi and Oh-gong's budding relationship despite these difficult circumstances. Oh-gong professes to be deeply in love with Seon-mi, but only because of the Geumganggo. He constantly reminds her that if she takes it off, his love will disappear, and he may return to wanting to eat her for immortality instead. Seon-mi, who has been a loner all her life, can't help but be touched by Oh-gong's thoughtful actions, and struggles to guard her heart against any romantic feelings because Samjang's tragic destiny is always to be a sacrifice for humanity against growing evil. Each episode involves Seon-mi and Oh-gong fighting off the demon of the week while dealing with their own internal conflicts. Seon-mi's feelings for Oh-gong are also constantly tested as she learns more about the kind of person Oh-gong is and his many secrets. The nightmare looming constantly over both their heads is a prophetic dream that Seon-mi had about the world ending, and knowing that she had to do everything she could to prevent it. Oh-gong later also learns that his role as Sam-jang's protector means he will either kill her, or she will kill him. This further drives them apart even as they fall more in love with each other.