In the near future, 10 percent of the population will consist of Humanoids—machines with advanced functions and artificial intelligence resembling human personalities, easily recognized by their sideways pupils. These specialized patients likewise require a special doctor. By day, Dr. Hikaru Sudou runs a medical clinic for Humanoids; by night, under the moniker of Moggadeet, he performs illegal procedures and gathers information about his lost mother.

Hikaru encounters patients with varying problems unique to this society: a Humanoid struggling with the question of whether she and the source of her backup data are the same person, a teenage Humanoid who cannot improve athletically, and even a robot teddy bear with memories of multiple owners. As the world's technology constantly evolves, newer and more complex questions surrounding humanity arise. With each new advance, it becomes more difficult to define what truly makes one human or Humanoid.