Lily is a quiet, observant girl who recently finished sixth grade. She has a habit of making herself "invisible" to avoid conflict, especially during arguments between her mother and older sister. Deeply connected to her Korean heritage through her grandmother's stories, Lily possesses a vivid imagination and a strong desire to protect her family.

Sam is Lily's teenage older sister who fiercely resents being uprooted from her California beach town. She sports a distinctive white streak in her hair to purposefully defy stereotypes about quiet Asian girls. Despite her prickly exterior and frequent texting, she struggles with the memory of their late father and the reality of her grandmother's declining health.

Mom is an accountant and single mother trying to manage her career while caring for her aging mother and two daughters. She operates with a sense of practicality and propriety, preferring logic over the magical stories her mother tells. Her sudden decision to move the family to Sunbeam stems from a deep, underlying concern for her mother's well-being.

Halmoni is Lily and Sam's Korean grandmother who lives in an ivy-covered cottage in Sunbeam. She is a respected community figure known for her herbal cures and deep knowledge of folklore. Harboring secrets about her past and experiencing sudden bouts of illness, she maintains a stubborn independence and relies heavily on traditional rituals to ward off bad spirits.

The Tigress is a massive, magical creature from Korean folklore who appears to Lily shortly after the family arrives in Sunbeam. Capable of manipulating the weather and remaining invisible to adults, she stalks Halmoni's house with a specific agenda. She presents a daunting challenge, offering supernatural bargains regarding Halmoni's health.

Ricky is an energetic, friendly boy wearing a bright orange shirt and black jeans who receives language arts tutoring at the local library. He comes from a wealthy family but struggles academically. Eager for connection, he quickly latches onto Lily's research and enthusiastically offers to help her build a tiger trap in her basement.

Jensen is a bubbly teenage library aide and language arts tutor in Sunbeam. She keeps a stash of snacks in the staff room for her students and quickly makes an impression on the Reeves sisters. Her welcoming demeanor provides a sharp contrast to the dreary Washington weather.

Joe is the local librarian in Sunbeam. He maintains a neat, orderly environment but also surprises patrons by baking excellent chocolate cupcakes for the staff room. He views the library not just as a place for classification, but as a space where stories connect people over time and space.

Andy is Lily and Sam's late father, who died in a car accident when Lily was four and Sam was seven. His absence leaves a profound impact on the family dynamic, particularly influencing Sam's fear of driving and the family's underlying grief. Halmoni recalls serving him milkshakes mixed with mud to keep him grounded.