Yumi is an 11-year-old Korean American girl living in Los Angeles who spends most of her free time helping out at her family's struggling restaurant, Chung's Barbecue. She feels like an invisible social outcast at her elite prep school, the Winston Academy, and constantly falls short of her parents' high academic expectations. Secretly, she dreams of becoming a stand-up comedian and meticulously records jokes in a hidden notebook.

Jasmine is an attractive and dynamic comedian with a popular kids' comedy tutorial vlog that Yumi obsessively watches. She conducts a summer comedy camp in Koreatown to help youngsters develop their improv and stand-up skills. She offers a permissive worldview focused on artistic growth, standing in contrast to the strict expectations of Yumi's traditional parents.

Yuri is Yumi's 20-year-old older sister, a brilliant student currently enrolled in medical school at UCLA. With a genius-level IQ, she serves as the family paragon and the primary subject of her parents' boasting. Despite her outward success, she wrestles with immense academic pressure and harbors deep doubts about her chosen career path.

Mr. Chung is Yumi's workaholic father who pours all his energy into running the family's Korean barbecue restaurant. He faces severe financial anxiety due to shifting demographics in Koreatown that threaten his livelihood. He is deeply motivated by a desire to provide his daughters with a secure, prosperous future.

Mrs. Chung is Yumi's mother, a pragmatic and deeply traditional woman who co-manages the family restaurant. She is intensely focused on prestige and academic achievement, viewing education as the only valid path to financial security. She frequently humblebrags about her daughters to customers and enrolls Yumi in intense summer courses to secure a prep school scholarship.

Mrs. Pak is the strict instructor at the local Koreatown hagwon where Yumi spends her summer afternoons cramming for the SSAT. Nicknamed "Pak Attack" by her students, she is known for her intense discipline and high academic standards. Despite her intimidating exterior, she pays close attention to the psychological hurdles her students face.

Ginny is Yumi's best friend and a fellow student at the local cram school. She is a pragmatic girl who generally accepts the traditional academic expectations placed upon her by her family. However, she asserts her own form of rebellion through a strict commitment to veganism, which frequently creates conflict with her mother.

Felipe is a friendly, outgoing Hispanic boy who attends the summer kids' comedy camp with Yumi. He is an avid comic book collector and a natural performer who quickly incorporates Yumi into his social circle. He provides Yumi with a glimpse of a peer dynamic entirely free from academic pressure.

Sienna is a student at the Haha Club's comedy camp whose parents work in the film industry. Yumi initially perceives her as living a highly privileged and perfect life. In reality, Sienna deals with neglectful parents who take little interest in her activities, making her friendships at the comedy camp deeply important to her.

Manuel is the dedicated cook at Chung's Barbecue. Having learned to make authentic Korean dishes from Mrs. Chung, he is an essential and loyal part of the family's struggling business. He is also the rare adult in Yumi's life who actively listens to her jokes and supports her comedic aspirations.