In a futuristic world, an assassin is killing the greatest robots in existence. One robot that passes for human is tasked with solving the crimes and avoiding the same fate in this epic pairing of two manga legends.

Tenma discovers two more pieces of the puzzle to Johan's past in Prague --- a story about Johan's mother, a beautiful woman taken away by the secret police, and an old recording of Johan as a child. And Tenma knows all too well that Johan is lurking close by.