The protagonist of the series, he is a Japanese neurosurgeon working in Düsseldorf, Germany. In spite of his Director's explicit orders, he decides to operate on a critically wounded boy instead of the city's mayor, which results in his demotion and the break-up of his engagement. He is, however, shortly promoted after the mysterious murders of three of his superiors, and continues working at the hospital until it is revealed to him that the boy he risked his career to save is, in fact, a mass murderer.
The Atoner: As kind-hearted as he is, he sees his absolute biggest mistake as being something he alone can fix. And despite numerous opportunities he gets where he could abandon his self-set mission, he refuses every time.
Badass Pacifist: He can take a beating, jump off a bridge to avoid confrontation, and save peoples while avoiding the police and criminals alike.
Big Good: This is particularly evident in arcs where he is offstage or not the main character. In keeping with his nearly messianic role, by the end, nearly all the characters would do anything to protect him.
Celibate Hero: Post-Eva, although there is some subtext involving Nina that may avert this. In Another Monster, it is explained that he was still quite the celibate during his high school years and even purposely didn't get together with a girl who liked him (and the feeling was somewhat mutual) merely because he was friends with her (cheating) boyfriend.
I'm Not Hungry: When he was captured by the police, he refused to eat for so long they had to put him on an IV. Which doubles as Fridge Brilliance, as he was trying to end up in the infirmary in order to get in touch with Gunther Milch.
Parental Favoritism: It's mentioned in Another Monster that his father favored him, his youngest son, over his other brothers. However, his mother favored his two older half-brothers (who are unrelated to her) more than him.
Skilled, but Naïve: Tenma's a surgical prodigy, but it's not his relative inexperience with a scalpel that gets him into trouble in the beginning. It's his inexperience with another aspect of being a doctor: hospital politics.
"Tenma the Weenie! Tenma the Weenie! He peed his pants, too!"
Even more so considering the full story given in Another Monster. After the first time the other boys scared him during hide-and-seek, Tenma decided to go through it again in order to conquer his fear. What ended up happening was that they couldn't find him and thought that he just went home, so when one of the mothers told them it was time to go home, they left Tenma by himself. When they found him still hiding in the abandoned yard at night, they probably stopped picking on him simply because he had the guts to do all that.
Technical Pacifist: Although he has no problem pushing, kicking, shoving, and threatening with violence, he has a hard time causing harm to others even if it is to defend his own life.
Think Nothing of It: Does not like to take credit for his achievements, e.g. denying that he'd saved the Turkish district.
The antagonist of the story, he is introduced (outside Tenma's TV, that is) as a ten-year-old with a bullet in his brain. Shortly after being saved by Tenma, he escapes from the hospital with his twin sister Anna. He resurfaces nine years later as a killer, admits to having poisoned Tenma's superiors, and proceeds to wreak havoc across Germany. His identity is unknown to the general public, and his murders are subsequently blamed on Tenma.He is alternately perceived note albeit mainly by delusional killers and neo-Nazis as a vampire, an alien, the Devil, and the next Hitler. Both the manga and the anime open with a passage from Revelation that refers to the Antichrist and mirrors several events from Johan's life.
Bitch in Sheep's Clothing: He's a great guy to hang out with, and a good listener, too! But not for long. He'll even shed Tender Tears when you tell your troubles. He'll also cheer up your ailing elderly parents better than you ever could, and get along better with your kids, too.
Cast as a Mask: The anime does this. To make the reveal that the pretty new girl in town is actually Johan more shocking, the studio used Nina's voice actress to play Johan whenever he dons this look. This is done both in the Japanese version and in the English dub.
Commie Nazis: Having grown up in an East German orphanage, he'd have been raised communist. This doesn't stop Neo-Nazis exalting him as the next Hitler. Bonus points for the Anti Christ motifs.
Truth in Television - the vast majority of Neo-Nazis in modern Germany are from the East German areas, which are harsher and poorer than the West. A lot of Neo-Nazis were disillusioned teenagers raised in a communist society.
Corruption by a Minor: Quite a few times, and we're not talking getting other kids to scrump apples here. Or just kids, for that matter. Inspires a taxi driver to emulate, uh, Taxi Driver without (thankfully) even going Lolicon about it, at the age of ten.
Dissonant Serenity: His default facial expression changes about twice in the series' entire run. Both times it makes him even more creepy.
The Dreaded: Every character who has knowledge of Johan is deathly afraid of him. One commits suicide when he's brought up too much in conversation and others start shaking uncontrollably just thinking about him.
Driven to Villainy: Horrifyingly. Sure, he was already an Enfant Terrible by as a child, but he was severely warped by the empathic bond that formed between his sister and him when they were still very young. While she repressed the psychological torture she'd gone through, he began to think it had happened to him instead... and thus from that seed a monster grew.
Even Evil Has Loved Ones: Though it is debatable on whether he's even capable of love, his obsession with Anna/Nina doesn't make it any less disturbing. However, it is notable that his greatest fear is forgetting about "Anna."
Irony: One of the reasons he became the guy he is, is due to the empathy he felt for his sister's traumatic experiences. That's right, compassion made him a monster.
I Want My Beloved to Be Happy: He does this for Anna/Nina twice. He willingly allows Anna to shoot him after finding out that he killed the Lieberts, and the reason behind his "perfect suicide" plan of a massacre in Ruhenheim along with eradicating his existence (mirroring Franz Bonaparta's Red Rose Mansion massacre, which is in itself an "expression of love" to the twins' mother) was partly due to how irredeemable he has become and to make Nina happy.
I Will Find You: One of Johan's goals is to reunite with Nina. He tries to make contact with her a few times, but either Tenma or Neo-Nazis who want Johan for their own benefit have a tendency to get in the way.
Meaningful Name: Apart from the context the name Johan has within the series, it is noteworthy that this is a version of John, whose Revelations provide the source for the series' epigraph. Although the St. John of Revelations is usually referred to as Johannes, a different (and more formal) German version of John. John is also one of the most stereotypically generic names, which may be a reference to his own lack of identity.
Parental Abandonment: There is a mystery behind what happened to the Liebert twins' biological parents. It's implied that their father was killed, but it's later revealed that the mother turns out to still be alive.
Villainous Breakdown/Villainous BSOD: After re-reading "The Monster With No Name" and again (offscreen) after Nina points out that some of "his" memories are actually hers. And once more when Nina forgives him in Ruhenheim and it becomes apparent that Tenma won't shoot him unless he actually threatens an innocent.
Wicked Cultured: This is part of what makes him so terrifying and effective. He is practically a genius knowing many languages with a keen understanding of law which he uses to Mind Rape a certain character and was even able to run a massive money laundering scheme at fifteen-years-old.
Johan's twin sister. After the incident in 1986, she is adopted by a couple from Heidelberg where she leads a normal life. When Johan decides to contact her again, Tenma foils his plan by helping Nina escape. Her foster parents are, however, killed by Johan's henchmen, and their murder sends her on a quest for vengeance, across Germany and the Czech Republic where she picks up the forgotten pieces of her past.
Action Girl: Played straight and later deconstructed. Being an Action Girl does not equal having the mental fortitude to match.
Bad Dreams: Before she recovers her memories of Johan, she has recurring dreams of a monster attacking her.
Celibate Heroine: There are a few guys in the series who seem to like her, but she either rejects them (Peter) or is outright oblivious (Lipsky). However, she does have some subtext with Tenma that may avert this.
Distressed Damsel: Subverted early in the series. Played straight several times later on in the series including one case where she is saved from certain death by the same man who murdered her step-parents., as a part of the deconstruction theme that is a huge part of Monster. Though double subverted as people constantly try to capture her as a hostage and bait for Johan, but she willingly allows it if it means reuniting with Johan and killing him.
Morality Pet: Subverted. She may be the one person in the whole world who Johan appears to care a great deal about and his greatest fear is forgetting about her, but he's not above mindraping her and nearly indirectly causing her to commit suicide. And her forgiving Johan doesn't stop the latter in wanting to get himself killed.
Mutual Kill: Once she regains her memories, her plan is to kill herself after killing Johan.
An agent of BKA (the German federal police), he is assigned to the case of the murders of the three Eisler Memorial officials. Believing Tenma to be the only logical suspect, but deterred by the lack of evidence, he resumes the investigation ten years later after an officer guarding one of Tenma's patients is killed using the same M.O. used on the three doctors. Personal pride, rather than an interest in justice, prompts him to chase Tenma across Germany and Czechoslovakia, concluding that 'Johan' is Tenma's alter-ego.
Agent Scully: So, Dr. Tenma, you're saying a ten-year-old fresh out of major brain surgery killed these people?
Ambiguous Disorder: He has a ridiculously impressive memory, but very strange mannerisms and is implied to obsess over closing his cases.
Busman's Holiday: Subverted in that when he finally takes a vacation, he turns down a request for assistance from the local authorities. Otherwise, not so much played straight as sneakily turned Up to Eleven.
Character Tics: His most distinguishing feature is his habit of moving his fingers as though he were typing, which helps him memorize information verbatim.
Not So Stoic: Thanks in part to his Character Development, Lunge gets angry when Roberto starts talking about his failed marriage and how his grandchild doesn't even know his biological grandfather. He gets another one soon after when he starts up a Shut Up, Hannibal! moment.
The daughter of the Eisler Memorial Hospital director, she is engaged to Tenma at the beginning of the series. When he falls out of favor with her father, she breaks off the engagement, but has a change of heart soon after Heinemann's death. Tenma's subsequent rejection leaves her embittered and with an advanced alcohol problem, and she spends the remainder of the story vacillating between love and hate for him.
From Bad to Worse: When waking up in a police cell with personal belongings missing, smoking someone else's cigarette butts off the ground outside the station just for the hit, and stealing booze from a panhandler is not the low point of her day, you know it's a steep downhill slope.
If I Can't Have You: Though she is kind enough to not actually try to kill him, she does attempt to put him in prison for life.
I Will Wait for You: Waits for Martin at the Frankfurt Central Station to run away with him. He doesn't make it.
Lady Drunk: Through most of the series. She eventually stops drinking as a token to Martin, who didn't like alcohol, and continues to order coffee instead of alcohol three years later in Another Monster.
Also known as Klaus Poppe, Emil Sebe, and by many other pseudonyms, Bonaparta is responsible for the eugenics program that resulted in the twins' birth. When he wasn't busy kidnapping his test subjects' mothers and killing their fathers, he engaged in educating the superior children with the aid of morally questionable fairy tales he had penned himself.
For Science!: Played partly straight, partly as a twisted excuse ("This is an experiment").
Heel-Face Turn: Rather a slow, maddening process in which he gives up his experiments and becomes a dull, old man, living incognito in a small town where he unsuccessfully tries to continue his creative pursuits.
By killing over forty people in front of your love interest's already traumatized child to give her a chance at a better tomorrow. But don't worry about how your Sadistic Choice affected her, or her other child; your books and the pedagogy you developed will help fix all that. Just leave your evil conspiracy in place, it'll be all right.
However, in Another Monster, it is implied that he had a hand in erasing the twins' mother's past, and Lipsky hints that perhaps his reasons behind it was to isolate the twins' mother so only he would know of her existence.
The Man Behind the Man: Bonaparta was the one in charge of the experiments at Kinderheim 511 and the readings at the Red Rose Mansion.
A perpetually smiling man searching for Franz Bonaparta, the man whose pedagogic theories formed the basis of the brainwashing program Grimmer had been subjected to as a child. Unable to feel emotion in his regular state (according to himself, although that doesn't stop him from trying to "fake it"), he transforms into a brutal and unstoppable alter-ego when under extreme duress.
Sociopathic Hero: He is this literally. In spite of his lack of emotion, he's a pretty nice guy who actually performs heroic deeds because he wants to. His Magnificent Steiner persona is the more traditional version of this, as it causes him to kill his enemies in a more brutal fashion.
Retired Badass: Used to work with the border police. This, being the West German border police during the Cold War, which was basically a paramilitary organization as they were expected to hold back a possible Communist invasion from the east, makes it even more Badass.
A former classmate of Tenma's, he is a leading criminal psychologist who attributes his proficiency to possessing the brain of a serial killer. After initially planning to turn Tenma over to the police, he realizes the latter's innocence and becomes, along his former professor Reichwein, an active helper in Johan's case.
Not So Different: He explicitly invokes this towards the incarcerated serial killers that he interviews, though one may feel that he exaggerates. Also backfires, possibly due to his tendency to get "research subject" mixed up with "research assistant," leaving him repeatedly wide open to Hannibal Lectures from the "subjects."
Love Martyr: He was this to the three women in his life: his alcoholic mother who died freezing in the cold because he left her there when he was a child, his drug-addict late girlfriend who committed suicide after he caught her cheating on him and refused to kill her, and Eva who he died protecting.
Hidden Depths: Gets quite serious about his gourmet cooking. Not to mention touchy about Tenma's apparently inevitable suggestion that whatever the dish, it could be improved by the addition of soy sauce. Seriously, this includes Chicken Marengo.
Dr. Jerk: While not incapable of empathy (see his scene with Eva), he generally displays a burned-out lack of human response, including endangering patients by turning up late for surgery, possibly due to dalliances with nursing staff.
Ensign Newbie: Very much so, constantly inspiring others to attempt mentoring him, generally to his annoyance. By the time Verdemann tries it, pointing out his professional and personal greenness verges on a Berserk Button.
Decoy Protagonist: Volumes 6-7 is one long day-in-the-limelight arc where the action shifts from Tenma to some new characters, which happens fairly often throughout the series. Initially, he seems to be the main character of this arc (Volume 7 is even named after him), but a tragic run-in with Johan causes the focus to shift to his therapist, Reichwein for the rest of the arc until Tenma returns.
Gory Discretion Shot: The fact that it's not revealed just how he dies makes the whole thing all the more maddening.
Spell My Name with an S: Braun would be the German version, but the Viz translation gives his name as Brown throughout.
Trauma Conga Line: He wasn't drunk when he shot Yost. He was completely sober and, upon seeing how the boy had become utterly depraved, shot him dead without remorse. To provide an alibi he drunk his ass off not long afterward, and forgot everything because of the combination of the trauma and the alcohol. Either way, his career was over and he started a new life. Things were looking up...until Johan forced him to remember and he commits suicide not long afterward. The kicker? The boy he shot came from 511 Kinderheim, so it was completely warranted for Braun to shoot him, but Johan's words were much too powerful.
Spell My Name with an S: The American broadcast went so far as to edit a poster in order to corroborate their mis-dubbing of his name as Schuwald. Schuwald is also the spelling used in the German edition of the manga.
An extremely talented lawyer known for always getting innocent verdicts. In fact, he only takes on clients if he believes they are innocent. Naturally, he ends up being Tenma's lawyer after he's arrested in Prague. His desire to free innocent people is rooted in his childhood, when his father was accused of being a spy.