"Seishun On Air" centers on a group of high school students who form a broadcasting club to create their own radio show. The protagonist, Haruto Aoi, is a reserved and introverted student with a passion for music and sound engineering. After stumbling upon an old radio transmitter in the school’s storage room, Haruto becomes inspired to start a radio program, despite his initial reluctance to step into the spotlight. Alongside him is Yui Shirakawa, a lively and outgoing classmate who dreams of becoming a voice actress. Yui’s enthusiasm and charisma help drive the project forward, balancing Haruto’s technical expertise with her creative energy.

The narrative explores the challenges of producing a radio show, from technical difficulties to creative disagreements, while also delving into the personal lives of the club members. As the group grows, they are joined by Riku Tendo, a former athlete struggling with an injury that ended his sports career, and Sana Mizuki, a quiet but observant student with a talent for writing. Each character brings their own struggles and aspirations to the table, creating a dynamic interplay of personalities and motivations.

The radio show becomes a platform for the characters to express themselves and connect with their peers, addressing topics ranging from school life to deeper emotional issues. Through their collaboration, the group learns to overcome insecurities, build friendships, and find their voices. The story also touches on themes of self-discovery, resilience, and the power of communication, as the characters navigate the complexities of adolescence and the pressures of pursuing their dreams.

As the series progresses, the club faces external challenges, such as competition from other school clubs and the threat of losing their broadcasting equipment. These obstacles test their resolve and force them to confront their fears and limitations. The narrative balances lighthearted moments of camaraderie with more serious reflections on personal growth, creating a well-rounded portrayal of high school life and the pursuit of creative passions.