In middle school, Arisu Yamabuki found comfort in a late-night radio show hosted by a girl who called herself Apollo. Her voice became his only solace, but one day, she stopped broadcasting without explanation and seemingly vanished. Now a high school sophomore, Arisu has dedicated himself to finding the girl behind that voice. His years of investigating have led him to one conclusion: Apollo is a student at the newly co-ed Furin High School.

His hunch proves partially correct when he hears the broadcasting club's first announcement. The voice on the school's speakers is unmistakably familiar, the voice he has been searching for. However, when Arisu bursts into the club room, his simple search becomes unexpectedly complicated. There are four girls in the club, and each one sounds like Apollo in a different way.

The four members are Rikka Inohana, an ambitious girl aiming to become a professional singer; Shinobu Uzuki, who dreams of working as a polished television announcer; Nene Himekawa, an aspiring voice actress with a sharp tongue; and Iko Kirino, a shy girl who wants to reinvent herself as a popular VTuber. Determined to uncover which one is his Apollo, Arisu joins the broadcasting club. He soon discovers that while each girl has a powerful voice and a big dream, they all lack the skills and polish to achieve their goals. Seeing their potential, Arisu takes it upon himself to help them improve, offering his support and resources. As he works alongside them, helping with everything from singing technique to on-camera presence, he continues his silent investigation, listening closely for the one clue that will reveal Apollo's true identity. The series follows this central mystery while exploring the distinct personal challenges and career aspirations of each girl, blending romantic comedy with the competitive world of voice-driven entertainment.