Sun-hee is a ten-year-old Korean girl who is keenly observant and bold. Despite traditional gender roles that demand she remain quiet and focused on domestic tasks, she actively seeks out information to understand the increasingly hostile world around her. She excels academically, winning awards for her mastery of the Japanese language and Kanji, while simultaneously nurturing a deep pride in her Korean heritage by recording her true thoughts in a private diary.

Tae-yul is a thirteen-year-old boy who struggles with traditional academic studies but excels at physical tasks and mechanics, particularly working on motor scooters. As the eldest son, he feels a heavy responsibility to protect his family under Japanese occupation. Fascinated by airplanes and deeply angered by the indignities his people suffer, he seeks direct, physical ways to push back against the oppressors.

Uncle is a vocal and deeply patriotic Korean man who runs a local print shop. Unlike his cautious brother, Uncle is impulsive and publicly expressive about his hatred for Japanese imperialism, eventually involving himself with an underground Korean resistance movement. He serves as a heroic archetype for his niece and nephew, teaching them forbidden knowledge like the true appearance of the Korean flag.

Abuji is the calm, rational patriarch of the family and a vice principal at the local school. He navigates the difficult position of working within the Japanese-controlled education system while trying to protect his family. His cautious and analytical demeanor often puts him at odds with the more hot-headed members of his family, who misinterpret his patience as compliance with the enemy.

Omoni is the soft-spoken, traditional mother of the household. Because she lacks formal education and does not speak Japanese, she relies heavily on her family to interpret the changing laws around them. Despite her quiet demeanor, she possesses a fierce inner strength and commits her own acts of quiet rebellion, such as secretly keeping a national Rose of Sharon tree in her garden.

Tomo is the son of the school's Japanese principal and a childhood friend of Sun-hee. Because of his Japanese heritage, he enjoys a privileged status and naturally gets swept up in the pro-war propaganda that excites the young boys in town. His long-standing friendship with Sun-hee complicates his worldview as the military occupation becomes more severe.

Mrs. Ahn is an elderly, widowed neighbor who is initially shunned by the community because she is considered "bad luck." She cannot speak Japanese and faces brutal treatment from soldiers during neighborhood "accountings." She demonstrates stubborn resistance by refusing to learn the oppressor's language beyond the absolute minimum needed to survive.

Pak Sung-joon is a young Korean girl whose family is new to the town. Her father works at the local bank, a detail that unexpectedly shifts the social dynamics when she visits Uncle's print shop with Sun-hee.

Jung-shin is one of Sun-hee's school friends. Their relationship becomes complicated when evidence suggests that her family might be chin-il-pa (Korean collaborators with the Japanese), forcing Sun-hee to evaluate the safety of their continued friendship.

Hee-wo is Jung-shin's older sister. When she is drafted to work for the Japanese army abroad but is instantly returned home, it signals to the community that her family likely holds special favor with the Japanese authorities.

Grandfather is the deceased patriarch of the family who dedicated his life to scholarly pursuits. He died of a broken heart shortly after Japanese soldiers forced their way into his home, humiliating him by cutting off his traditional Korean top-knot and stealing his hard-earned jade button of scholarship.

Onishi-san serves as the military attaché assigned to the local school. His primary duty is to ensure that all students are adequately indoctrinated as obedient citizens of the Japanese Empire, frequently disrupting classes to enforce obedience and fear.