Jin is a Chinese-American boy who faces cultural isolation and discriminatory assumptions from both peers and teachers at his predominantly White school. He wants to fit in and frequently feels frustrated by the differences that set him apart from his classmates. He develops close friendships with other marginalized students but struggles with his own self-acceptance as he grows older.

The Monkey King is a deity who rules over the monkeys of Flower-Fruit Mountain. He studies kung-fu relentlessly, mastering four major heavenly disciplines to acquire immense strength and magical abilities. After a heavenly guard denies him entry to a dinner party simply because he is a monkey, he experiences profound embarrassment and rage. He begins forcing his monkey followers to wear shoes and violently demands respect from other deities.

Wei-Chen is an immigrant from Taiwan who immediately seeks out Jin for friendship upon arriving at his new school. He speaks perfect English but is less familiar with American social norms. Unlike Jin, he feels completely comfortable with his Asian heritage and ignores the derogatory insults directed at him by others. He provides a loyal and steady presence in Jin's life.

Danny is a White high school student trying to live a normal teenage life. He plays basketball, studies with his friends, and wants to fit in with the mainstream crowd at Oliphant High School. His social life is continually upended by the annual visits of his cousin, which repeatedly force Danny to switch schools out of sheer embarrassment. He lives in a state of high anxiety, dreading the humiliation his relative brings.

Chin-Kee is Danny's visiting cousin. He arrives wearing traditional Chinese clothing and speaks loudly in heavily accented, broken English. He behaves in brazen, attention-seeking ways, excelling academically while simultaneously performing extreme cultural stereotypes that embarrass Danny in front of his peers. He shows no self-consciousness about the discomfort he causes and stubbornly insists on attending classes with Danny every day.

Tze-Yo-Tzuh is the benevolent creator of the universe. He monitors the actions of all deities, demons, and spirits, sending emissaries to maintain order. He attempts to reason with the Monkey King, explaining that all creations are wonderful and trying to stop the deity's violent rampage across the heavens by demonstrating his omnipresent power.

Suzy is a middle school student of Japanese descent who attends school with Jin. Early on, classmates spread false rumors about her solely because she shares Asian heritage with Jin. She later dates Wei-Chen and faces intense emotional pain when other students target her with racist slurs, demonstrating the heavy toll of ongoing microaggressions.

Amelia is a White middle school student and the subject of Jin's intense crush. She is cheerful and values kindness in others. She accepts an invitation to go on a date with Jin, completely unaware of the social friction her decision causes among some of her White friends.

Greg is a popular White student with blond curly hair whom Jin admires enough to alter his own hairstyle. While he initially appears to be an ally who protects Jin, his protective instincts later take a confusing turn. As they reach middle school, he privately asks Jin to stay away from Amelia, citing his desire for her to make good choices.

Wong Lai-Tsao is a famously humble monk who lacks typical monastic skills. He cannot fast or meditate for long periods, and his preaching is largely ineffective. However, he shows extraordinary compassion by bringing fruit to vagrants every day and tending to their injuries, which earns him divine favor and a mission to the West.

Melanie is Danny's high school friend and study partner. She values her platonic relationship with Danny and gently rebuffs his attempts to ask her out on a date, wanting to protect their friendship. She remains friendly even after witnessing the chaotic arrival of Danny's cousin.

Steve is a large, athletic high school student who plays basketball with Danny. Remembering how he was bullied for his weight as a freshman, he offers to defend Danny from anyone who gives him trouble. His kindness is tested when he becomes the unwitting victim of a repulsive prank.

Mrs. Greeder is Jin's third-grade teacher at Mayflower Elementary. She incorrectly introduces Jin to the class and repeats offensive assumptions about his background, failing to provide a safe or welcoming environment for her new student.

Peter is an older student at Mayflower Elementary. He acts aggressively toward Jin and forces him to play offensive games, though Jin confusingly views Peter as his first friend in his new neighborhood before Peter moves away.

Timmy is a student at Mayflower Elementary who casually repeats racist stereotypes and slurs. His bigoted comments go largely unchecked by authority figures and cause deep emotional pain for the Asian students in his class.

Charlie is Jin's older cousin. Because Jin feels he cannot turn to his traditional parents for advice about American adolescent social norms, he consults Charlie for guidance on dating and personal hygiene.

Ao-Kuang is the Dragon King of the Eastern Sea. He intends to execute the Monkey King for trespassing in heaven until the Monkey King transforms into a terrifying giant and demands submission.