"Beck" centers on Yukio Tanaka, a 14-year-old boy leading an uneventful life in suburban Tokyo. His mundane existence takes a dramatic turn when he saves a strange dog named Beck from a group of delinquents. This encounter leads him to meet Ryusuke Minami, a charismatic guitarist who recently returned from the United States. Ryusuke introduces Yukio, nicknamed Koyuki, to the world of rock music, sparking a transformative journey for the young protagonist.

Koyuki begins learning to play the guitar under Ryusuke's guidance, gradually developing a passion for music. He forms a band called "Beck" with Ryusuke, bassist Taira Yoshiyuki, drummer Saku Yoshito, and later, vocalist Chiba Tsunemi. The band's journey is marked by struggles, growth, and the pursuit of recognition in the competitive music industry. Koyuki's personal growth parallels the band's evolution, as he navigates challenges such as self-doubt, relationships, and the pressures of balancing school with his musical ambitions.

The narrative explores the dynamics within the band, highlighting their camaraderie, conflicts, and shared dreams. Ryusuke's mysterious past and his connections to the American music scene add depth to the story, while Koyuki's relationship with Maho, Ryusuke's half-sister, introduces themes of young love and emotional vulnerability. As Beck gains traction, they face setbacks, including lineup changes, financial difficulties, and the harsh realities of the music business.

The series culminates in Beck's performance at the Greatful Sound festival, a pivotal moment that tests their resolve and showcases their growth as musicians. The story balances the band's professional aspirations with the personal lives of its members, offering a grounded portrayal of the challenges and triumphs of pursuing a creative passion. Through its focus on music, friendship, and self-discovery, "Beck" provides a compelling exploration of youth, ambition, and the transformative power of art.