Eric is a middle school student at Branton Middle School who acts as the perceptive but often quiet observer of his friend group. Nicknamed "Frost" after writing an award-winning poem inspired by Robert Frost, he struggles to find his specific place among his friends. He lives with his mother following his parents' recent divorce, making him highly sensitive to shifts and silences in his environment.

Wolf is a thoughtful, musically inclined middle school student who acts as the voice of reason within his friend group. Nicknamed after Wolfgang Amadeus Mozart, he displays maturity but is also highly sensitive to the hurtful actions of others. He easily empathizes with people, making him particularly vulnerable to the cruel words circulating around the school.

Deedee is a middle school student of Indian descent who fully embraces his "geek" label through his love of pop culture and tabletop games. He serves as the Dungeon Master for his friend group's Dungeons & Dragons campaigns, inspiring his nickname. Highly expressive and prone to finding drama in everyday situations, his small stature and open emotions make him a frequent target for school bullies.

Bench is an athlete who historically struggles to excel at his chosen sports, earning his nickname by frequently sitting on the sidelines. He provides a sense of physical protection for his less athletic friends, keeping them safe from physical intimidation. As he begins to experience success on the football field, his shifting interests threaten his bond with his long-time friends.

Rose is a new student at Branton Middle School who disrupts the established dynamic of Eric's friend group. Muscular and independent, she ignores traditional middle school gender expectations and refuses to let others dictate her choices. She creates origami figures, specifically fish, and quickly assumes a protective role over her new friends when they face intimidation.

The Bullies consist of three boys (Cameron, Noah, and Jason) who operate as a unified front to intimidate other students at Branton Middle School. They target vulnerable students like Eric's friend group to mask their own insecurities. They exploit the school's new sticky note trend to escalate their cruelty from physical shoves to targeted verbal attacks.

Ruby is a student at Branton Middle School whose single action serves as the catalyst for the entire story. After a science teacher accuses her of cheating, she sends a profanity-laced text message complaining about the incident. Getting caught sending this message prompts the school administration to implement a strict cell phone ban.

Mr. Sword is an English teacher at Branton Middle School who attempts to teach his students about the weight and permanence of language. In response to the growing sticky note trend, he assigns the class to write meaningful aphorisms. He quietly tries to protect his students from the negative consequences of their communication by throwing away intercepted notes unread.

Eric's mother is a newly single parent adjusting to life after a recent divorce. She provides a quiet, somewhat somber home environment for Eric and occasionally drives his friends around. Her old high school yearbooks offer Eric a glimpse into how social dynamics and relationships change over time.

Eric's father recently moved out of the family home following a divorce. Before leaving, he gifted Eric a book of Robert Frost's poetry, which directly inspired the poem that earned Eric his permanent nickname.

Wolf's mother provides transportation for her son and his friends after school. She facilitates the boys' ability to work together on their assigned nuclear arms race project by driving them home.

Bench's mother handles phone calls at the family home. She casually provides Eric with information about Bench's whereabouts, unintentionally revealing that Bench lied to his friends about his plans.