Johan Liebert is the older twin son of the Lieberts, whose father Michael was an East German trade advisor who defected to the West. He is the titular "monster" and the main antagonist of the series. The mystery of his past is the focus of the plot. He is called a monster, the next Adolf Hitler and the devil himself.

Johan was shot in the head as a child when his parents were killed in their home, but saved from death by [Dr. Tenma](https://anilist.co/character/718). Because of this, he regards Dr. Tenma almost as though he was his father. He claims to love his twin sister [Anna](https://anilist.co/character/720), and has some loyalty to her. Johan has spent parts of his life in different places under different names. He possesses charisma and intelligence but is also cunning, manipulative and deceitful; while he is seemingly kind, compassionate and loving to children, he is actually cold, cruel and fundamentally incapable of empathy. He uses his talents to manipulate and corrupt others, often with no apparent end than to cause suffering and destruction.

His goal, as he stated when he was young, is to kill everyone that knows of his existence, and be the last one standing at the end of the world. He identifies with other killers, discovering their secrets. One of the themes of Monster is how individuals are capable of transforming into monsters; Johan often acts as both a direct and indirect catalyst for this transformation.
~! During his "perfect suicide" he was shot in the head by a bystander and seemingly died, but was later saved by Kenzo Tenma. !~

Dr. Kenzo Tenma is a renowned Japanese brain surgeon working at a leading hospital in Germany. One night, Dr. Tenma risks his reputation and career to save the life of a critically wounded young boy over that of the town mayor who had been planning to support the hospital financially. A string of mysterious murders begin to occur soon after the operation, and Dr. Tenma emerges as the primary suspect despite no incriminating evidence. 
 
A doctor is taught to believe that all life is equal; however, when another series of murders occur in the surgeon's vicinity, Dr. Tenma's beliefs are shaken as his actions that night are shown to have much broader consequences than he could have imagined. Leaving behind his life as a surgeon he embarks on a journey across the country to unravel the mystery of the boy he saved.

**Height:** 160cm

[Website](https://nozomusasaki.com/) | [Twitter](https://twitter.com/nozomu_s_staff)

On March 28, 2020, he announced that he had graduated from the Faculty of Law at the University of Tokyo, while working as a seiyuu.

[Website](https://www.keithsilverstein.com/) | [Twitter](https://twitter.com/SilverTalkie) | [Instagram](https://www.instagram.com/keithsilverstein/) | [Facebook](https://www.facebook.com/keithsilversteinvo) | [TikTok](https://www.tiktok.com/@keithsilversteinva)

Keith David Silverstein is an American voice actor, best known for his roles as Johan Liebert in Monster, Vector the Crocodile in the Sonic the Hedgehog video games, Robert E.O. Speedwagon in JoJo's Bizarre Adventure, Hisoka in the 2011 version of Hunter × Hunter, Oogai Mori in Bungo Stray Dogs. He is also known from several non-anime roles, including Gabriel Agreste a.k.a. Hawk Moth (Shadow Moth in later seasons) in Miraculous: Tales of Ladybug & Cat Noir, and Zhongli in Genshin Impact.

__Affiliation:__ CJ ENM Voice Actors 5th Class (2003-2006)

**Height:** 173 cm (5'8")
**Agency:** Himawari Theatre Group

[Profile](https://profile.himawari.net/view/1542) | [Twitter](https://twitter.com/U_Yutopan) | [Wiki (en)](https://en.wikipedia.org/wiki/Y%C5%ABto_Uemura)

Everyone faces uncertainty at some point in their lives. Even a brilliant surgeon like Kenzo Tenma is no exception. But there’s no way he could have known that his decision to stop chasing professional success and instead concentrate on his oath to save peoples’ lives would result in the birth of an abomination. The questions of good and evil now take on a terrifyingly real dimension.
 
Years later, in Germany during the tumultuous post-reunification period, middle-aged childless couples are being killed one after another. The serial killer’s identity is known. The reasons why he kills are not. Dr. Tenma sets out on a journey to find the killer’s twin sister, who may hold some clues to solving the enigma of the “Monster.”
 
(Source: VIZ Media)