In a world where 'Toys' grant unique powers, some use them for detective work while others turn to thievery. Detective academies train individuals to combat phantom thieves, like the renowned group 'Milky Holmes'. But when their powers vanish during a battle with the phantom thief Arsene, the group's future is jeopardized. Now, Sherlock, Nero, Hercule, and Cordelia must reclaim their abilities within three months to avoid expulsion. Tantei Opera Milky Holmes follows their quest to restore their Toys and adapt to a new reality devoid of their defining powers.