The series follows Dr. Kenzo Tenma as he pursues a young psychopath/sociopath named Johan, whose life Tenma had once saved. The story rapidly progresses through a number of locations: it starts in Düsseldorf, Germany, passes through Berlin, Frankfurt, Munich, Wiesbaden, cities in the Czech Republic such as Prague, and other cities and villages.
Both the anime and the manga begin with a passage from The Revelation of St. John the Divine, Chapter 13: Verses 1 & 4:
And I saw a beast rise up out of the sea, having seven heads and ten horns, and upon his horns ten crowns, and upon his heads, the names of blasphemy. And they worshipped the dragon which gave power unto the beast: and they worshipped the beast, saying, “Who is like unto the beast? Who is able to make war with him?”
The quote is often interpreted as the coming of the Antichrist. This quote is used because of the many parallels and comparisons between one of the main characters of Monster (Johan) and two candidates of the Antichrist as predicted by Nostradamus.
The text on the cover of the first volume reads as follows:
“Düsseldorf, West Germany in 1986. One day, Dr. Kenzo Tenma ignored his boss’s order and executed a humanitarian rescue of a man’s child. That’s how this horrible story begins!!”
Dr. Kenzo Tenma is a young Japanese doctor working at the Eisler Memorial Hospital in Düsseldorf during the 80s. A highly accomplished brain surgeon, he appears to have everything on his plate: a promotion in the offering; the favor of the director of the hospital Heinemann; and Heinemann’s daughter Eva as his fiancée. However, Tenma grows increasingly dissatisfied with the political bias of the hospital for treating patients, and seizes his chance to change things after a strange massacre brings the twins Johan and Anna Liebert into his hospital. Johan has a gunshot wound to the head and Anna keeps muttering about killing, and Tenma decides to operate on Johan instead of the mayor of Düsseldorf, who arrived afterwards. Johan is saved, but Mayor Roedecker dies. Tenma loses all his social standing and Eva as a consequence. However, Heinemann and other doctors in Tenma’s way are mysteriously murdered, and both children disappear from the hospital soon after. The police suspect Tenma, as he benefits greatly from this turn of events, but they have no evidence, and so can do no more than question him.
At this point, the story advances to seven years later. Tenma is now the Chief of Surgery at Eisler Memorial Hospital. However, he is about to come face to face with a sociopath – a sociopath that he helped save.
A known criminal is found on the street, hit by a car. He comes under the care of Dr. Tenma, who observes him muttering about a “Monster”. Tenma extends kindness to that criminal, and thus the criminal begins to open up for Tenma. Then one evening when Dr. Tenma comes back with a clock as a gift for the criminal, he finds the guard in front of the criminal’s room dead, and the criminal himself gone.
Following his trail to the construction site of a half finished building near the hospital, he finds the man. The man, who has developed a sort of doctor-patient friendship with Dr. Tenma, warns him against coming closer, and pleads with him to run away. Tenma refuses, however, and the identity of the man holding the gun pointed at the criminal in the abandoned parking garage is revealed to be the boy whose life Tenma had saved nine years ago – Johan Liebert. Despite Dr. Tenma’s attempt to reason with him, Johan shoots the criminal, tells Tenma that he could never kill the man who had saved his life, and then walks off into the night while Tenma is still too shocked to stop him. After this incident, Tenma is again suspected by the police, particularly Inspector Runge, and he tries to find more information about this ‘Johan’. He soon discovers that the boy’s sister, now named Nina, happily living the life of an adopted daughter to two caring parents, and the only trace of her terrible past are few dreams she has had. Tenma discovers her on her birthday, and manages to prevent her from meeting her brother, but comes too late to prevent Johan from murdering her foster parents. As the story progresses, Tenma learns of the origins of this monster, from the former East Germany’s attempt to use a secret orphanage called Kinderheim 511 (where Johan came from) in order to create the “perfect soldiers” through “psychological reprogramming”, to the author of a children’s book which was used in a eugenics experiment in Czech Republic. He also learns about the scope of the atrocities this “Monster” has committed, and he vows to fix the mistake he made when he saved Johan’s life.
While Tenma is the main character of Monster, the story also focuses heavily on those surrounding his search for Johan, such as Inspector Runge (who is investigating Johan’s various murders but pins them all on Tenma) and Nina Fortner (aka Anna Liebert, Johan’s twin sister), and a host of other characters, minor and major, whose lives have been shaped by the deeds of the monster named ‘Johan’.