Sophie is a 14-year-old girl who lives with her father in Miami and visits her mother in Congo during the summer. Struggling to reconcile her American upbringing with her Congolese heritage, she makes impulsive decisions out of a desire to help. When war breaks out, her resilience, adaptability, and knowledge of three languages become critical to her survival.

Otto is a young bonobo, approximately three and a half to four years old, who was taken from his family by a bushmeat trafficker. He arrives at the sanctuary malnourished, covered in sores, and missing a finger. Affectionate and mischievous, he relies heavily on Sophie as a surrogate mother and initially struggles to socialize with other apes.

Florence is Sophie's mother and the dedicated founder of a bonobo sanctuary outside Kinshasa. Born and raised in Congo, she possesses a warm, tough personality and easily puts both humans and animals at ease. Her profound devotion to conservation causes tension with her daughter, as she frequently prioritizes the apes' welfare over her family.

Anastasia is a four-foot-tall adult female bonobo and the matriarch of the sanctuary's adult group. Raised in a human household before moving to the sanctuary, she enforces the social hierarchy with a strict, sometimes aggressive demeanor. She prefers her role as alpha female over her maternal duties.

Mushie is a male bonobo occupying a lower position in the adult group's hierarchy. Despite his low status, he proves helpful and protective by constructing sleeping nests out of branches. He harbors a crush on the matriarch and seeks her affection.

Songololo is a young female bonobo and the biological daughter of Anastasia. Because her mother frequently rejects her, she often seeks attention and affection elsewhere. She is playful and quickly forms a bond with Otto.

Patrice is a dedicated staff member at Florence's sanctuary who assists with veterinary care. He monitors the news during the political unrest and attempts to coordinate Sophie's safe evacuation from the country.

Bouain is a teenage rebel soldier who was forced into the army after his school was attacked. He wears a necklace of human fingernails to signify his power. He views Otto as sharing half his soul and claims ownership of the ape in the city.

Wello is a quiet older man who operates a small boat on the Congo River. He trades for food along the riverbanks and agrees to transport Sophie partway to her destination in exchange for future payment.

Clément is a local driver employed by the bonobo sanctuary. He is cautious and pragmatic, locking the car doors when Sophie spots an animal trafficker on the road.

Mama Brunelle is one of the workers in the sanctuary's nursery who cares for the baby bonobos. She provides Sophie with serious, practical advice on how to bandage and treat Otto's wounds.

Mama Marie-France is a dedicated worker in the sanctuary's nursery. She helps to care for the infant bonobos and is deeply emotionally invested in their well-being.

Ikwa is an older male bonobo in the adult enclosure. Named after a village near the release site, he shares quiet, peaceful moments with Sophie, often sitting on branches with her to watch the sunset.

Pweto is a lone male bonobo with a missing ear, a hole in his cheek, and a crippled arm. He lives in isolation because the matriarchs attacked him after he accidentally dropped an infant bonobo.

Banalia is an adult female bonobo who shows early signs of acceptance toward Sophie, joining her under a rain poncho during a storm.

The schoolmaster runs a boys' boarding school hidden in the jungle. He is protective of his students, using a fake disease warning sign to deter soldiers, and generously provides Sophie with supplies.

Hector is a man coordinating helicopter evacuations. He passes along a message from Florence but refuses to let Sophie bring Otto on the evacuation flight.

The animal trafficker is a local man trying to survive by selling bushmeat and infant apes. His actions highlight the dire poverty in the region and the constant threat to the bonobo population.

Sophie's father is Florence's ex-husband who lives in Miami, Florida. He video-chats with Sophie to stay connected and provide support from across the world.