"Rainbow Signal: Hi-Fi Set" is a short anime series that revolves around the lives of four young men—Touma, Shou, Haruto, and Yuuto—who share a passion for music and form a band called Hi-Fi Set. Each character brings a distinct personality and musical talent to the group, creating a dynamic interplay of relationships and creative energy. Touma, the guitarist, is the most serious and driven, often acting as the de facto leader. Shou, the vocalist, is cheerful and outgoing, balancing the group's mood. Haruto, the bassist, is quiet and introspective, while Yuuto, the drummer, is playful and carefree, often lightening the atmosphere.

The narrative explores their journey as they navigate the challenges of pursuing their musical dreams while balancing personal struggles and interpersonal dynamics. The series delves into their individual backstories, revealing the motivations and insecurities that shape their identities and contributions to the band. As they work together to compose and perform music, they confront conflicts, misunderstandings, and moments of growth, both as individuals and as a collective unit. The story emphasizes themes of friendship, perseverance, and the transformative power of music, portraying how their shared passion helps them overcome obstacles and strengthen their bond.

The anime is structured around their performances, rehearsals, and personal interactions, blending moments of humor, drama, and heartfelt emotion. While the series is concise, it effectively captures the essence of their journey, offering a glimpse into the challenges and rewards of chasing a creative dream. The characters' development is central to the narrative, with each episode highlighting their evolving relationships and the impact of their music on themselves and their audience. "Rainbow Signal: Hi-Fi Set" presents a straightforward yet engaging portrayal of youthful ambition and camaraderie, anchored by its focus on music and the connections it fosters.