Cath is an 18-year-old college freshman who writes wildly popular fanfiction for the Simon Snow fantasy series. She experiences significant social anxiety, preferring the safety of her online community over real-world interactions. Deeply loyal to her family, she feels betrayed by her twin sister's desire for independence and struggles to adapt to the demands of college life.

Wren is Cath's identical twin sister who embraces the college experience with a desire for independence. Outgoing and eager to separate her identity from her twin's, she pushes boundaries by partying and drinking heavily. She attempts to cope with their shared childhood trauma by acting out rather than retreating into fictional worlds.

Levi is an agricultural sciences student who grew up on a ranch and hopes to work in range management. Known for his constant smile and friendly demeanor, he goes out of his way to be kind to everyone. He struggles academically due to difficulties with reading, but he is incredibly patient and genuinely interested in Cath's fanfiction hobby.

Reagan is Cath's older, more experienced college roommate. She is blunt and fiercely protective, adopting a mentoring role toward her younger roommate. Though she occasionally finds Cath's habits strange, she genuinely cares for her wellbeing and pushes her to experience life outside the dorm room.

Professor Piper is a published author and college fiction-writing instructor. She recognizes Cath's immense talent but maintains a strict, traditional view of literature. Viewing fanfiction as derivative and unoriginal, she pushes her student to write stories drawn from her own life.

Nick is an upperclassman in Cath's fiction writing course. He writes dark, gritty stories and asks Cath to collaborate on writing exercises with him in the library. He presents himself as an intense, serious writer but relies heavily on Cath's editorial skills to improve his clichéd drafts.

The twins' single father works in advertising and experiences bipolar disorder. He is deeply loving and supportive of his daughters' hobbies, but his manic episodes and tendency to stop taking his medication mean he often relies on them for care and stability.

The twins' mother abandoned the family when the girls were eight years old. Her sudden reappearance during their freshman year of college forces the family to confront old wounds and differing desires for reconciliation.

Courtney is Wren's college roommate. She is highly social and embraces the college party scene, joining Wren in a restrictive weekday diet so they can drink heavily on the weekends.

Abel is Cath's boyfriend from high school. He is reliable and steady, providing a comfortable, passionless relationship that allows Cath to avoid true emotional vulnerability.

Jandro is Wren's college boyfriend. He is protective of her and actively disapproves of her heavy drinking, offering a stabilizing presence in her otherwise chaotic social life.

Simon is the orphaned, magical protagonist of the fictional Simon Snow series. As the chosen one, he attends a school of magic and battles evil forces. He serves as the primary subject of Cath's popular fanfiction, where she explores his hidden depths and romantic potential.

Baz is Simon Snow's mysterious classmate and archrival in the canon series. In Cath's fanfiction, he harbors secret identities and vulnerabilities, becoming a complex romantic counterpart to Simon.

Gemma T. Leslie is the British author of the wildly popular Simon Snow fantasy books. Her impending release of the final book in the series creates a ticking clock for Cath's own fanfiction ending.