Juliette is the 19-year-old heir to the Scarlet Gang. She prefers American-style dresses and possesses a fierce temper that she cultivates to maintain a dangerous reputation in the city. Deeply loyal to her family and city, she struggles with the violent expectations of her gang while desperately trying to prevent mass casualties from a new monstrous threat.

Roma is the heir to the Russian White Flowers gang. Formerly averse to bloodshed, he adopts a hardened, ruthless persona following a perceived betrayal, wearing all-white suits and slicking his hair back. He struggles intensely with his lingering feelings for Juliette while mourning the supposed loss of his best friend.

Kathleen/Celia Lang is Juliette’s cousin and a pragmatic operative for the Scarlet Gang. She is a trans woman who balances her family's demands with her own growing political awareness, increasingly sympathizing with the working-class Communist movement. She frequently acts as a spy and messenger, prioritizing her loyalty to Juliette over the gang as an institution.

Rosalind Lang is Juliette’s cousin and Kathleen/Celia's sister. Because she carries the Lang surname rather than Cai, she often feels excluded from the Scarlet Gang's true inner circle. This insecurity makes her desperate for validation and a place of her own, leading her to make risky choices and harbor dangerous secrets.

Benedikt Montagov is Roma's loyal cousin and a talented artist. Following the apparent death of his closest friend, he is consumed by profound grief and impulsiveness. His sorrow drives him to reckless behavior and fuels an intense desire for revenge against the Scarlet Gang.

Marshall Seo is a gregarious, playful member of the White Flowers. Thought dead by most of the city after the events of the previous months, he secretly hides in a safe house to protect his friends. Despite his isolation, he maintains a cheerful demeanor and secretly guards his loved ones from the shadows.

Tyler Cai is Juliette's cousin and her chief rival for the leadership of the Scarlet Gang. He is calculating and ambitious. He genuinely believes in the blood feud, taking pleasure in aggressive tactics against the White Flowers while constantly questioning Juliette's fitness to rule.

Alisa Montagov is Roma's perceptive younger sister. Though too young to be a full combatant for the White Flowers, she frequently spies on adult conversations to gather information. She serves as a grounding, reasonable presence for her brother during the city's escalating violence.

Dimitri Voronin is a ruthless and ambitious member of the White Flowers who challenges Roma's position as heir. He frequently deals with European allies and seeks personal glory, constantly maneuvering for more power within the gang hierarchy.

Lord Cai is the patriarch of the Scarlet Gang and Juliette's father. He attempts to manage the shifting political climate of Shanghai by aligning the gang with Nationalist forces, prioritizing institutional survival and wealth over the traditional street-level blood feud.

Lady Cai is Juliette's mother and Lord Cai's wife. She frequently attempts to moderate Juliette's Westernized habits and maintains strict expectations about family loyalty, appearance, and duty within the Scarlet Gang's upper echelons.

Lord Montagov is the leader of the Russian White Flowers and Roma's father. He maintains a cold, pragmatic approach to gang leadership, demanding absolute loyalty and ruthlessness from his heir while managing the gang's illicit enterprises.

General Shu is a powerful leader within the Kuomintang (Nationalist) army. He represents the growing political military power in Shanghai that threatens the traditional gang structures, imposing strict demands on those seeking his alliance.

Pierre Moreau is a French ally of the White Flowers. He becomes a key figure of interest when Juliette and Roma investigate the new wave of monstrous attacks plaguing the city.

Lourens is an elderly scientist who assists the protagonists. He studies the monstrous bugs and attempts to develop a reliable vaccine to protect the citizens of Shanghai from the deadly contagion.

Paul Dexter is the deceased architect of the original monstrous contagion in Shanghai. Though dead, his scientific research and the remaining monstrous insects continue to threaten the city under new direction.

Walter Dexter is Paul Dexter's father. He arrives from England looking to profit off his son's deadly scientific research by offering it to the highest bidder before fleeing the volatile city.