Legend has it that after the Earth was destroyed, the master clockmaker Y constructed a replacement world using cogs and gears. Naoto Miura is a young boy who dreams of becoming a great clockmaker. Yet, despite his unique talent—acute hearing that allows him to instantly grasp clockwork mechanics from sound alone—he has achieved little progress. This changes when a coffin drops from the sky into his apartment, revealing RyuZU, a female automaton crafted by Y himself. RyuZU's arrival brings Marie Bell Breguet, the talented heir to a prestigious lineage of clockmakers, and her cyborg bodyguard Vainney Halter into Naoto's life. When both she and Naoto find themselves caught in a life-threatening, action-packed battle, they uncover an unsettling truth: the clockwork planet humanity has inhabited for over a millennium is starting to fail—a secret that many are willing to kill to keep hidden.