Dedicated to all players who want to learn about the backstory.

[火花]

Actually, there are many interpretation videos on the Chinese internet.
In the story of Zhu Bajie, my personal interpretation is:
Zhu Bajie:
Zhu Bajie fell for a leading figure among the Chang'e (this is mentioned in Zhu Bajie's game story, "A group of Chang'e fairies in plain clothes entered the scene from the back," and "Among them, a fairy in a white dress and white hair, danced gracefully.") (Chang'e is a general term for the maids of Taiyin Zhenjun). During his pursuit (perhaps courtship), Zhu Bajie encountered the Purple Spider. Later, he accidentally witnessed the white-haired Chang'e meeting privately with the Jade Emperor (or the Jade Emperor's son). As a result, Zhu Bajie was punished by the Jade Emperor's guards and banished to the mortal world, where he was reincarnated as a pig.
In the animation, when Zhu Bajie woke up, he met Gao Cuilan (not the Purple Spider) at Gao Laozhuang, where she was seeking a husband and eventually chose Zhu Bajie.
Later, when the four went on their journey to retrieve the Buddhist scriptures from the West, they passed through the Spider Cave, where Zhu Bajie reunited with the Purple Spider but did not dare to recognize her (as the gods in heaven were constantly watching over them during their journey). Similarly, after defeating the Hundred-Eyed Demon Lord, he still couldn't acknowledge her. In the end, they had a daughter together, and during the journey, Sun Wukong asked Zhu Bajie to kill the remaining spiders, but Zhu Bajie spared the Purple Spider’s life (according to speculation based on the story). Throughout this plot, Zhu Bajie dared not acknowledge the Purple Spider, fearing that the heavenly court would punish her and their daughter (the story of Bull Demon King and Spider Sister Four in Chapter 5 is a good example of this).
(Speculation) As a side note, during the Bull Demon King's storyline, Zhu Bajie killed the Bull Demon King's old lover, the Jade-Faced Fox, and arrogantly proclaimed it. To explain, the Jade-Faced Fox was a spy for the heavenly court, and Zhu Bajie was also helping the Bull Demon King. Sun Wukong was also speaking ill of the Bull Demon King to make things appear proper for the heavenly court, but in secret, he whispered in the Bull Demon King's ear, "Acknowledging our master is the only way out." After hearing about the Jade-Faced Fox, the Bull Demon King decided to rebel against the heavenly court on his own.
Easter egg: Some online have analyzed the last lyrics of the animation, "We meet in the next life," with the male voice saying, "Please don't look back," and the female voice singing, "Please remember to glance back."

Now, let's talk about Sun Wukong and Sister Four, with some interesting analysis:
In the predecessor to Black Myth called <DouZhanShen>, the White Bone Spirit was Sun Wukong's wife. (Before the 100-chapter version of Journey to the West, Sun Wukong always had a wife, and each new version was a reinterpretation based on the original.)
In an old Chinese animation, Sun Wukong and the Purple Fairy, one of the Seven Fairies, had mutual feelings for each other. When Sun Wukong’s leg was trapped by golden shackles, the Purple Fairy stole a diamond from the Queen Mother of Heaven and gave it to Sun Wukong, freeing him. In the end, they helped each other but never dared to confess their feelings.
Similarly, in Stephen Chow's movie A Chinese Odyssey, Sun Wukong and Zixia Fairy also had mutual affection but could not be together in the end.
(Speculation) After repeatedly helping Sun Wukong, the Queen Mother banished the Purple Fairy to the mortal world, where she became the White Bone Spirit. After many trials, Sun Wukong was made to forget the Purple Fairy by the heavenly court. During the chapter of "The Three Fights with the White Bone Spirit," she tried multiple times to recognize Sun Wukong, but in the end, the forgotten Sun Wukong killed her.
(Speculation) In the game, Sister Four is the reincarnation of the White Bone Spirit. She helped the fated protagonist multiple times despite the opposition of the heavenly court. In one chapter, Sister Four gave the protagonist some treasures, possibly the dowry she once intended for Sun Wukong. There is also the character Qinlang Xian (one of the masterminds behind the Spider Cave, but also a henchman for the heavenly court). Sister Four was controlled by the heavenly court, sealed with purple talismans. In the end, she was captured by the heavenly court and said to Sun Wukong, "Leave quickly," not wanting him to get involved. If you continue forward and tear off the talisman, the heavenly court will capture her. (Hurry up and release the DLC; I want to storm the heavenly court!)

Bull Demon King:
The Bull Demon King was once one of Sun Wukong's good brothers. Sun Wukong, a great demon, had six good brothers before embarking on the journey to retrieve the scriptures, and the seven of them were known as the "Seven Great Saints," namely:

Bull Demon King, Great Sage Who Pacifies Heaven,
Demon King Jiao, Great Sage Who Overturns the Sea,
Roc Demon King, Great Sage Who Confounds Heaven,
Lion Camel King, Great Sage Who Moves Mountains,
Macaque King, Great Sage Who Commands the Winds,
Baboon King, Great Sage Who Drives Gods,
Sun Wukong, Great Sage Equal to Heaven.
They once rebelled against the heavenly court but were eventually defeated.
Red Boy, the son of the Bull Demon King, set up his own territory, with the sole desire to eat Tang Sanzang's flesh. As a mischievous child, he transformed into a boy to deceive the four disciples and eventually captured Tang Sanzang. Yes, just like the little fox in the game. Many Chinese players knew immediately it was Red Boy.
Sun Wukong, as the sworn brother of the Bull Demon King, tried to use their relationship to get his master back, but Red Boy didn't believe him and obstructed the journey. They fought, and Sun Wukong eventually asked Guanyin to subdue Red Boy (perhaps also to help the Bull Demon King).
After Sun Wukong brought Red Boy into Buddhism, the Daoist faction (the heavenly court) was unhappy and revealed Red Boy's true identity to the Bull Demon King (Red Boy was not the Bull Demon King's biological son; the heavenly court had made Iron Fan drink water, and she gave birth to a Yaksha).
The Bull Demon King became deeply disappointed and eventually left home, encountering the Jade-Faced Fox, whom he later married into.
Sun Wukong needed the fan of the Bull Demon King's wife to get through the Flaming Mountains (only the Banana Fan could extinguish the flames). The couple had separated, but Sun Wukong barged in. Iron Fan Princess, still resentful over the Red Boy incident, refused to give it. Sun Wukong then transformed into the Bull Demon King and tricked the fan away. When the Bull Demon King found out, he turned into Zhu Bajie and stole the fan back. Zhu Bajie slaughtered the Jade-Faced Fox's entire household (the Jade-Faced Fox was a spy for the heavenly court, sent to seduce the Bull Demon King, which Zhu Bajie likely figured out, as he hadn't done anything like this earlier in the story).
However, the Bull Demon King didn't know the full story. First, they harmed his son, then insulted his wife, and finally killed his concubine. Unable to endure the humiliation, he rebelled against the heavenly court. The heavenly court then came to behead the Bull Demon King (though demon kings don't die from beheading, at least the Bull Demon King wouldn't). Iron Fan Princess couldn't bear to see it and offered the Banana Fan, choosing to submit to Buddhism along with the Bull Demon King, bearing the humiliation.
Later, when Sun Wukong's descendants were slaughtered and he once again stormed the heavenly court, the Bull Demon King, driven by family revenge or other motives, joined Erlang Shen in killing Sun Wukong. In Sun Wukong's dying words, the Bull Demon King finally understood. Everything Sun Wukong had done to his son and wife was to show the heavens, aiming to protect the Bull Demon King. In the end, Sun Wukong concealed everything, allowing the Bull Demon King to take the credit, but the Bull Demon King felt immense guilt.
Eventually, the heavenly court revealed Red Boy's identity, and together with Sun Wukong's body, the Yaksha clan (who were wiped out by Buddhism, leaving Red Boy as the last survivor). Red Boy, now aware of his identity and mission, asked the Bull Demon King for Sun Wukong's body, intending to wage war against Buddhism (Buddhism had wiped out the Yaksha clan but had taken in Red Boy, a case of psychological torment).
This is my interpretation. For every thousand people, there is a different Hamlet. Journey to the West is a myth that can be interpreted in many ways.

written in Chinese, created by AI translation. If there are any inaccuracies (whether in the plot or translation), please forgive me. — The English translation may differ.