Carmen is a 15-year-old girl of Puerto Rican American descent living in Bethesda, Maryland. She acts as the central connective tissue for her group of friends, organizing their gatherings and cherishing their collective bond. She looks forward to a quiet summer with her father in South Carolina but is unexpectedly thrust into a suburban household with his new fiancé. This sudden change deeply unsettles her, prompting impulsive reactions as she tries to process her feelings of isolation.

Lena is a naturally beautiful teenager traveling to Greece to connect with her heritage. Her physical appearance often draws unwanted attention, causing her to adopt a guarded, introverted demeanor to protect herself from superficial judgments. She hopes to bond with her extended family but finds herself hindered by a language barrier with her grandfather and her own deeply ingrained shyness.

Tibby is a witty and cynical teenager spending her summer at home in Bethesda. Feeling neglected by her parents in favor of her younger siblings, she adopts a rebellious, sarcastic exterior. She originally plans to film a mocking documentary about the people she encounters at work, but her perspective shifts when she forms an unlikely bond with a young girl facing a serious illness.

Bridget is a highly energetic and athletic teenager known for her fearless approach to life. She throws herself into activities with relentless intensity, often acting without considering the consequences. Beneath her confident and thrill-seeking exterior, she carries unaddressed grief regarding the loss of her mother, leading her to seek out risky situations and external validation.

Carmen's father, who moved away after divorcing her mother. He invites Carmen to South Carolina for the summer, but surprises her with the news that he is engaged and living with his new fiancé's family. He avoids addressing the resulting tension directly, hoping everyone will naturally get along.

Kostos is a college student studying in London who spends his summer helping his grandfather at the local forge in Greece. He approaches Lena with respect and genuine interest, though his attempts to connect are initially met with suspicion and hostility due to a misunderstanding.

Eric is a 19-year-old college sophomore working as a coach at the soccer camp. He draws Bridget's immediate attention. He attempts to maintain a professional distance, but his boundaries are frequently tested by Bridget's relentless flirtation and blatant disregard for camp rules.

Bailey is a 12-year-old girl battling leukemia. Despite her severe illness, she maintains a vibrant, curious outlook on life. She inserts herself into Tibby's film project, using her empathetic nature to draw out the humanity in the subjects Tibby originally intended to mock.

Al's fiancé, a blonde woman living in a large suburban house. She attempts to integrate Carmen into her household but is met with deep resistance. She focuses heavily on planning her upcoming wedding and maintaining a cheerful atmosphere.

Lydia's teenage daughter. She is blonde and petite, forming a physical contrast to Carmen. She attempts to share her living space with her future stepsister but is met with hostility, particularly when struggling with her algebra homework.

Lydia's teenage son. He is observant of the household dynamics and occasionally calls Carmen out on her antagonistic behavior. He plays soccer and deals with the absence of his own father, who is currently in a rehabilitation facility.

Lena's grandfather. He speaks only Greek, which limits his ability to converse with Lena. He shares his granddaughter's quiet, proud nature, leading to a silent but deeply felt connection between them that transcends language.

Lena's grandmother, who speaks fluent English and acts as a translator and mediator in the household. She frequently fawns over Lena's beauty and actively tries to push her into social situations with local boys, particularly Kostos.

Lena's younger sister who accompanies her to Oia. She provides a sharp contrast to Lena; she is extroverted, easily forms connections with locals, and is openly enthusiastic about romance and taking risks.

A teenager who spends his time setting high scores on the Dragon Master arcade game. Tibby initially views him as a loser, but his calm self-assurance and genuine interest in his hobby challenge her prejudices as she films him for her documentary.

Bailey's mother. She manages her daughter's illness with grace and occasionally contacts Tibby to update her on Bailey's medical condition, expressing gratitude for their friendship during a difficult time.

A handsome and popular boy in Bethesda. He serves as Tibby's initial crush, though she finds herself unable to articulate what she actually likes about him beyond his physical appearance.

The manager at Wallman's drugstore. He is strict and frequently reprimands Tibby for minor infractions, making him the initial target of her satirical film project.

A coach at the Baja California soccer camp. She expects teamwork and discipline from her players and grows increasingly frustrated with Bridget's selfish and showy behavior on the field.

Kostos's grandfather, who runs the local forge in Oia. He expects Kostos to take over the family business and finds himself drawn into a physical altercation with Lena's grandfather over a misunderstanding.

A teenage girl attending the soccer camp in Baja California. She quickly befriends Bridget and encourages her rebellious exploits without fully understanding Bridget's underlying grief.

Another camper in Baja California who befriends Bridget. She participates in late-night excursions and reinforces Bridget's reckless behavior.

Carmen's mother, who lives with her in Bethesda. She provides a stable home environment and acts as a sounding board, helping Carmen understand the root of her anger toward her father.

Tibby's mother, who returned to a conventional lifestyle after having Tibby. She relies heavily on her eldest daughter to help manage the household while raising two younger children.

Tibby's father, who recently secured a demanding job at a prestigious law firm. His frequent absence leaves a gap in the household that Tibby is expected to fill.

Tibby's younger sister. Her presence in the house contributes to the chaotic environment that Tibby is eager to escape by working at Wallman's.

Tibby's baby brother. Like Katherine, he demands a significant amount of his parents' time and energy, fueling Tibby's resentment of her home life.

Bridget's late mother, who suffered from severe depression. Her absence profoundly affects Bridget's reckless behavior and avoidance of her grief.

Bridget's father. Following his wife's death, he struggles to connect with his daughter, leaving Bridget to rely heavily on her friends for emotional support.

Bridget's sibling. They share the tragedy of their mother's loss but maintain a somewhat distant relationship as Bridget seeks fulfillment outside her family.

Tibby's pet guinea pig. Tibby uses Mimi as a barometer for her own mental state, spending hours staring into the cage when she is feeling depressed or aimless.

A cashier at Wallman's who has exceptionally long fingernails. Tibby initially plans to use her as a target for her satirical film, but eventually learns that Angela carries her own personal grief.

A woman who has worked at the local movie theater for decades. She becomes a subject for Tibby and Bailey's documentary project and is eager to share her love of films.