The four Yuzuki brothers—Hayato, Mikoto, Minato, and young Gakuto—lost their parents two years ago and now work to raise themselves. Together they live, learn, fight, and forgive as brothers should.

The year is 2045. Singing is forbidden, and an AI system called MiucS creates music in place of people. Seria Aiba, a high school girl who can see spirits, lives quietly under these rules—until one day, she hears a real human voice singing. Following the song, Seria discovers the source: a ghost. Now Seria must decide whether to stay silent or risk everything to bring music back to the world.