Katrina is a young transgender runaway who escapes a traumatic household to seek refuge in the city. She carries a battered violin that represents her enduring passion for music despite her lack of formal training. Plagued by anxiety and low self-worth, she has difficulty asserting her own needs or trusting the people around her. Her unpolished musical talent eventually draws the attention of a notorious classical instructor.

Shizuka is a renowned violin teacher known in classical music circles as the "Queen of Hell." Decades ago, she struck a bargain with a demon that requires her to deliver the souls of seven violin students. Having already delivered six, she searches desperately for her final student as her deadline rapidly approaches. Despite her ruthless reputation, she possesses an awkward charm and unexpected capacity for empathy.

Lan manages a Los Angeles donut shop while secretly operating as the captain of an alien refugee family from a collapsing Galactic Empire. She fiercely protects her children but maintains a rigid, emotionally distant exterior to cope with their displacement. She uses her business as a cover to construct a stargate out of the giant donut sculpture on the roof.

Lucy runs a struggling, formerly prestigious violin repair shop in Los Angeles. She possesses natural talent as a luthier but grew up marginalized by her patriarchal family because of her gender. Operating in the shadow of her grandfather's tyrannical rules, she battles feelings of inadequacy despite her immense skill with stringed instruments.

Tremon is a demon who holds the contract to Shizuka's soul. He presents himself as an unsettling but impeccably dressed human, monitoring Shizuka's progress in finding her seventh student. He maintains a firm grip on his end of the bargain, constantly reminding his client of her impending deadline and relishing his control over human ambitions.

Shirley is Lan's eldest daughter and functions as a highly sophisticated holographic projection of a sentient computer program. She assists with the daily operations of Starrgate Donut and possesses vast technological capabilities. Her non-organic nature causes friction with her mother, leaving her questioning the validity of her own emotions.

Markus is Lan's teenage son and a brilliant engineer. He resents their family's refugee status and harbors intense anger about being trapped on Earth. His frustration often manifests as hostility toward the humans who frequent their shop and the mundane tasks he must perform to maintain their cover.

Aunty Floresta is an older relative living with the Tran family at Starrgate Donut. She brings a warm and caring presence to the household, often stepping in to provide the emotional support that Lan has difficulty offering. She possesses a keen intuition regarding human behavior and Earth's customs.

Windee is one of Lan's precocious young twins. She possesses advanced mathematical and computational skills, aiding her family with complex calculations for their ship and stargate project while adjusting to life on Earth.

Edwin is Lan's young twin son. He demonstrates a unique sensitivity to human culture, specifically regarding the nuances of Earth food. His intuitive understanding of taste proves essential to the family's attempts to successfully run a human donut shop.

Tamiko is a privileged and highly trained young violinist obsessed with achieving fame. She eagerly seeks to become Shizuka's next student, viewing the older woman's cruel reputation as a glamorous stepping stone to legendary status in the classical music world.

Astrid serves as Shizuka's loyal housekeeper and confidante. She manages the daily operations of Shizuka's home and provides practical support to her employer, maintaining a calm demeanor even when introduced to unusual situations or unexpected houseguests.

Evan is a film student who initially offers Katrina a place to live in Los Angeles. He maintains a facade of liberal beliefs but quickly proves to be manipulative and abusive, exploiting Katrina's vulnerable position as a runaway without resources.

Andrew is Lucy Matía's son. He recognizes the immense talent his mother possesses and harbors resentment toward the older generations of their family for marginalizing her. He supports her work and eventually takes an active interest in the luthier craft.

Catalin is Lucy Matía's deceased grandfather and the former patriarch of the Matía violin shop. His portrait looms over the workspace, serving as a constant reminder of the strict patriarchal traditions that systematically excluded female family members from the luthier craft.