@SJUGRAD13 Pluto is a retelling of an Astro Boy story (the 2nd arc of the manga: "The Greatest Robot on Earth"), told from the perspective of one of the minor characters in said story.
Basically, there's 6 other Robots in Astro Boy that are just as, if not more powerful than Astro Boy/Atom.
Something starts killing them, along with human beings. But all the robots are programmed not to kill.
One of the robots, Geschit, looks like a regular human, and works as a police detective in Germany. Pluto is story of him trying to figure out who is killing the 7 robots, since he is one of them.
It's one of the greatest manga I've ever read.