Four high school girls form a band to save their school's music club, despite one member's complete lack of musical experience. Yui Hirasawa, a cheerful but uncoordinated student, joins the Light Music Club at the urging of her new friends Mio Akiyama, Ritsu Tainaka, and Tsumugi Kotobuki. Their goal is to keep the club active and prevent its disbandment, but Yui must first learn to play the guitar, a task made more challenging by her initial inability to even hold the instrument properly. The narrative follows their humorous attempts to practice, write songs, and navigate the everyday life of high school students.

The first volume of K-ON! establishes a lighthearted and comedic tone, focusing on the formation of a high school band and the everyday lives of its members. The narrative emphasizes character interactions and humorous situations arising from their inexperience and personalities, particularly Yui's. Readers often respond positively to the charming character dynamics and the gentle, slice-of-life pacing. The series is known for its feel-good atmosphere and its exploration of friendship through the shared experience of music.