At the start of a new school year at Sainotama Girls High School, three childhood friends are reunited after attending different middle schools. The energetic and impulsive Nozomu Tanaka, who is famously bad at both academics and reading social cues, decides to pass the time by giving everyone in their class a nickname based on their most defining trait. Her sensible otaku friend Akane Kikuchi is dubbed Wota, a nod to her obsession with manga and yaoi. Their other companion, the stoic and highly intelligent Shiori Saginomiya, is called Robo due to her emotionless, mechanical demeanor. In retaliation for her antics, Tanaka herself is christened with the nickname Baka, which means idiot, and it sticks immediately.

The live-action series follows the daily, often pointless, conversations and adventures of these three girls alongside their uniquely eccentric classmates. The core storyline does not follow a grand narrative but instead focuses on the humor of wasted youth, exploring the quirks of each character as they navigate school life. Among their friends is Saku Momoi, called Loli, who has the appearance of a child and fiercely resents being treated like one. Minami Yamamoto, known as Yamai, is a chunibyo who wears an eyepatch and believes she is a half-blood warrior battling a secret organization. The shy but mathematically brilliant Kanade Ninomae, nicknamed Majime for her serious demeanor, is secretly a boyish-looking girl who is oblivious to her own popularity. The class also includes the occult-obsessed shut-in Hisui Kujyo, called Majo, and the beautiful half-Austrian transfer student Lily Someya, who claims to be allergic to men but shows a confusing interest in Baka. Their long-suffering homeroom teacher, Masataka Sawatari or Waseda, is a young man with a secret life as a Vocaloid music producer, much to the hidden admiration of Wota.

Major narrative arcs typically revolve around the fallout of Baka's thoughtless but often well-meaning schemes, such as her disastrous attempts to find a boyfriend or her brutal honesty that somehow helps a struggling ramen shop owner and his daughter. The arc involving Lily focuses on her strange allergic reaction to Baka and her increasingly intense attempts to get closer to her, much to the confusion of the rest of the class. Another significant arc explores the friendship between Majime and Robo, as Majime desperately tries to find a way to connect with someone she views as an intellectual equal. The series builds toward moments of genuine friendship, culminating in the class banding together to prevent Baka from having to repeat a year due to her failing grades. The tone remains a fast-paced, character-driven comedy that celebrates the aimless and absurd moments that define high school life.