Sky is a seventeen-year-old girl entering public school for her senior year after being homeschooled entirely without modern technology. She experiences emotional numbness during physical intimacy and considers herself a mature, independent thinker. An avid long-distance runner, she values her solitary routines but remains fiercely protective of the few close friends she allows into her life.

Dean is an athletic senior who has recently returned to school following a rumored stint in juvenile detention. He carries a reputation as an unpredictable outsider with a short temper, though he frequently demonstrates deep emotional sensitivity. He bears a noticeable "Hopeless" tattoo on his forearm and uses long-distance running to process his intense feelings.

Karen is Sky's adoptive mother who maintains a strict, technology-free household, banning televisions, smartphones, and the Internet. She makes her living selling homeopathic medicines and herbal remedies at local flea markets. Her eccentric, highly insulated lifestyle choices create occasional friction as Sky attempts to explore typical teenage social circles.

John is a local police chief and Sky's biological father who placed her in foster care following the death of his wife. He became a single parent after a fatal car accident and ultimately chose not to raise his daughter alone. He remains an estranged figure in Sky's present-day life.

Six is Sky's outgoing, sexually adventurous best friend and primary link to typical teenage social dynamics. She prepares to leave for a study abroad program in Italy shortly after the school year begins. She provides Sky with a secret prepaid cellphone to ensure they can maintain contact despite Karen's household rules.

Brecklin is a cheerful, openly gay high school student who views himself as a social outsider. He proactively seeks out Sky to form an alliance against the school's more hostile cliques. He pays close attention to school gossip but maintains an optimistic attitude.

Grayson is a confident teenage boy who attempts to initiate a physical relationship with Sky. He fancies himself highly attractive but fails to read Sky's clear lack of interest, repeatedly overstepping her boundaries before giving up.

Les is Dean's deceased twin sister whose death by suicide a year prior casts a long shadow over her brother's life. Her passing dictates much of Dean's current emotional instability and defensive behavior.

Jack is Karen's longtime romantic boyfriend. He supports her small business endeavors and maintains a steady, accommodating presence in the household's unusual dynamic.

Lorenzo is a young man Six meets almost immediately after arriving for her study abroad program. He quickly becomes the focus of her romantic attention overseas, serving as a distraction during her travels.