Joan is a 36-year-old attending physician in the medical Intensive Care Unit of a large New York City hospital. She stands just under five feet tall and possesses a highly introverted nature, preferring the reliable hum of hospital machines over unpredictable human interactions. A child of Chinese immigrants, she values meritocracy and hard work above all else, regularly taking on extra shifts to avoid empty hours in her apartment.

Fang is Joan's brother, eight years her senior. Educated at Yale, he works as a highly successful hedge fund manager and lives on a sprawling 10-acre compound in Connecticut. He is intensely focused on accumulating wealth to secure his family's standing in the United States, viewing financial success as the ultimate triumph over the difficulties his immigrant parents faced.

Mark is a former publishing employee who recently moved into Joan's building. He is highly extroverted and overly familiar, often assuming a level of closeness that makes Joan uncomfortable. He frequently attempts to integrate himself into Joan's life by baking pies, gifting her unwanted furniture, and offering unsolicited opinions on her experiences.

Joan's mother is a resilient Chinese woman who relocated back to Shanghai after raising her children in the United States. She exhibits a stoic, emotionally distant demeanor, showing care through practical actions rather than physical affection. Following the death of her husband, she travels back to the United States for an extended visit with her son's family.

Tami originally immigrated to the United States to obtain a master's degree but chose to abandon her academic track to marry Fang and start a family. As a stay-at-home mother to three children, she runs an orderly, affluent household. She holds traditional expectations for women and frequently expresses irritation at Joan's disinterest in marriage and motherhood.

A hardworking immigrant who owned his own construction firm, Joan's father prioritized career success over emotional warmth. He suffered a fatal stroke during a business meeting. His legacy heavily influences both of his children, instilling in them an immense drive to succeed and a shared philosophy of forging new paths.

Reese is an attending physician at the hospital who relies heavily on his conventional good looks and charm. He maintains a warm relationship with the hospital's human resources department and guards his personal time fiercely, refusing to work holidays. His approach to medicine and workplace politics sharply contrasts with Joan's strict focus on merit.

Madeline is a 34-year-old German attending physician who works alongside Joan. She lives in an apartment filled with plants alongside her long-term boyfriend. She demonstrates genuine care for Joan's wellbeing, gently suggesting she take walks to fill her time off.

The director oversees the attending physicians at the hospital. He is highly appreciative of doctors who take on heavy workloads, making him a strong supporter of Joan, though he eventually enforces mandatory leave policies for her own good.