Naoki Urasawa’s Monster is a psychological thriller built around one terrible decision. Dr. Kenzo Tenma saves the life of a young boy named Johan Liebert instead of treating the town’s mayor, believing he is simply doing what is right. Years later, Tenma discovers that Johan has grown into a ruthless criminal, forcing him to confront the consequences of the life he chose to save.
The anime series has earned its reputation through its gripping mystery, characters, and thoughtful look at morality and human nature. Its slow-burning suspense and approach to crime make it different from many other anime in the genre. Still, several series offer similar experiences through their dark stories, complex characters, psychological tension, or morally difficult choices.
1. Pluto Explores Humanity Through a Gripping Murder Mystery
A string of murders gives Pluto an intriguing starting point. Detective Gesicht is tasked with investigating the deaths of several humans and robots, only to discover that the case is connected to something much larger than a series of crimes. The deeper he goes, the more complicated the truth becomes.
Created by Naoki Urasawa with Takashi Nagasaki and based on Osamu Tezuka’s Astro Boy, Pluto takes its murder mystery into a futuristic world filled with advanced robots and artificial intelligence. The 2023 anime tells its story across eight feature-length episodes. This gives the investigation plenty of time to develop its characters and emotional stakes.
That science-fiction setting may seem far removed from Monster, but the two series share an important quality. Both use a mystery to explore what makes people capable of kindness, hatred, and violence. Pluto also spends considerable time examining grief, prejudice, war, and whether machines can truly experience human emotions.
Gesicht is another major reason the series should appeal to Monster fans. Like Dr. Tenma, he is not defined by flashy action or an exaggerated personality. His determination, empathy, and willingness to keep searching for the truth make him compelling.
2. Death Note Turns Intelligence Into a Battle of Wits
Light Yagami is an exceptionally smart student who believes he can create a better world. Everything changes when he finds the Death Note, a notebook that can kill anyone whose name is written inside it. He soon begins using its power to eliminate criminals and reshape society according to his own vision.
His actions attract the attention of L. L is a brilliant detective determined to discover who is behind the deaths. From there, the anime becomes a tense battle of wits, with both characters constantly trying to predict and outsmart each other.
The supernatural premise makes Death Note much more fantastical than Monster, but the psychological tension feels familiar. Neither Light nor L can rely on physical strength to win. They have to study each other, anticipate their opponent’s next move, and manipulate the people around them.
Fans who enjoyed watching Tenma slowly uncover the truth about Johan may enjoy Death Note. The series makes investigation and deduction a major part of its story. Light and Johan are very different characters, but both are highly intelligent. Their ability to manipulate others also makes them extremely dangerous.
3. Psycho-Pass Turns Criminal Investigation Into a Question of Free Will
Imagine living in a world where a computer can decide whether you might become a criminal before you actually commit a crime. That is the central idea behind Psycho-Pass. The anime is a dystopian thriller that turns crime prevention into a much bigger question about free will and morality.
The series takes place in a future where the Sibyl System constantly monitors people’s mental states and measures their potential for criminal behavior. Police officers use these readings to identify and deal with people who are considered dangerous. What sounds like a perfect way to prevent crime quickly becomes much more complicated as the characters begin to question whether the system can understand human nature or not.
Psycho-Pass revolves around Akane Tsunemori as she begins her career as a police inspector. Alongside enforcers such as Shinya Kogami, she investigates dangerous criminals while gradually discovering uncomfortable truths about the society she is supposed to protect. Shogo Makishima, one of the series’ central antagonists, makes the investigation even more difficult because he challenges the very system that labels people as criminals.
4. 91 Days Turns Revenge Into a Slow-Burning Crime Thriller
What happens when someone loses everything and decides that revenge is the only thing left to live for? 91 Days explores that question through a mafia story where every decision can come with deadly consequences. The series keeps its focus on the personal cost of revenge as its protagonist becomes more deeply involved in a dangerous cycle of violence.
The action anime series follows Avilio, a young man whose family is killed during a mafia conflict. Years later, he receives a letter that gives him a chance to return to Lawless and get close to the people responsible. He begins working his way into the Vanetti family’s criminal world, carefully hiding his real intentions.
What makes the story interesting is how little Avilio can trust the people around him. Everyone has their own plans, secrets, and reasons for staying alive. Even when characters appear to be allies, there is always the possibility that they could turn against each other.
Both anime avoid relying on supernatural powers to create tension. They also keep action scenes from becoming the main focus. Instead, the suspense comes from characters making difficult choices and hiding important information. Their decisions keep you guessing about who can be trusted.
The two stories also take revenge seriously. 91 Days does not treat Avilio’s mission as a path toward satisfaction. As he gets closer to his goal, the emotional cost of revenge becomes increasingly difficult to ignore.
5. Paranoia Agent Turns Everyday Anxiety Into Something Terrifying
Satoshi Kon’s Paranoia Agent introduces Lil’ Slugger, an attacker who targets people across Tokyo. At first, he appears to be a straightforward criminal, but the more the police investigate, the stranger the case becomes. His attacks seem connected to the personal problems and fears of the people he encounters.
The real appeal of the series comes from how it handles its antagonist. Lil’ Slugger is not a villain who appears to cause trouble and disappear. His presence becomes connected to the anxiety, pressure, and emotional struggles experienced by different characters. As the story progresses, it becomes increasingly difficult to separate reality from perception.
That psychological element makes Paranoia Agent a strong choice for fans of Monster. Johan is terrifying because of the way he affects people’s minds and pushes them toward destructive choices. Paranoia Agent follows a similar idea, although it presents the concept in a much more surreal way.
The 13-episode series also refuses to tell its mystery in a completely straightforward manner. It moves between reality, imagination, and symbolism, forcing viewers to question what they are seeing. Instead of treating fear as something that can be defeated, the anime looks at why people sometimes use fear as a way to escape their problems.
6. Odd Taxi Hides a Serious Mystery Behind a Colorful World
A taxi ride may not sound like the beginning of a serious crime mystery, but Odd Taxi turns everyday conversations into clues. The series follows Hiroshi Odokawa, a quiet walrus-like taxi driver who spends his days driving passengers around the city. His passengers slowly become connected to a missing-girl case. As Odokawa learns more, ordinary conversations begin to reveal important details about the mystery.
The setting is one of the first things that makes the anime stand out. Its characters are anthropomorphic animals, and the bright, casual presentation can make the anime look like a light comedy at first. The atmosphere changes as Odokawa’s ordinary taxi rides begin revealing secrets about the people around him.
The crime mystery works because almost every conversation has a purpose. A passenger who seems unimportant at first may become relevant later, while a small detail from an earlier episode can suddenly make sense much later. The mystery is built around these connections rather than constant action or dramatic reveals.
As the mystery develops, the cheerful surface starts to feel different. The characters begin to reveal their loneliness and personal struggles. Deception, crime, and hidden motives also become increasingly important to the story. These darker elements give the series much more weight than its unusual character designs suggest at first.
7. Erased Turns a Childhood Mystery Into a Race Against Time
Sometimes the biggest mysteries are hidden in memories from childhood. Erased uses that idea to tell a murder story that is as much about protecting people as it is about finding the truth. The plot of the anime combines suspense, emotional stakes, and a race against time to prevent a tragedy.
The time travel series revolves around Satoru Fujinuma, a struggling manga creator who has a strange ability that sends him back in time just before a tragedy happens. When a terrible incident changes his life, Satoru suddenly finds himself back in his childhood. This gives him a chance to uncover the truth behind a series of murders involving children.
The major theme is the desire to change something that should never have happened. Satoru knows that someone close to him is in danger, but he does not know who is responsible or how to stop the tragedy. His investigation becomes a race against time as he tries to understand the past and protect the people around him.
Satoru is also a big part of the anime’s appeal. He is not a traditional action hero. He is an ordinary young man who finds himself dealing with something far beyond his experience. His determination to protect his childhood friends makes the mystery feel personal rather than being about solving a crime.
8. Terror in Resonance Builds a Mystery Around Two Dangerous Outsiders
Two teenagers carrying out terrorist attacks are not the usual protagonists of an anime thriller. Terror in Resonance puts Nine and Twelve at the center of its story. The series slowly reveals their past and the reasons behind their actions. Their choices create a dangerous conflict that becomes harder to control.
The anime starts with a series of carefully planned attacks in Tokyo. The police, led by detective Kenjirou Shibazaki, try to figure out who is responsible and what they are up to next. At the same time, viewers get to know Nine and Twelve, making the story less about catching criminals and more about understanding their motives.
The biggest difference is the scale and pacing. Monster is a long, slow-burning story that follows Tenma across different places and introduces a large cast of characters. Terror in Resonance tells a much shorter story, with only 11 episodes, and puts greater emphasis on atmosphere, trauma, and the relationship between Nine and Twelve.
9. Moriarty the Patriot Turns a Famous Villain Into the Main Character
William James Moriarty does not see himself as a criminal. He wants to change a society where the wealthy have power and the poor are treated as less important. To achieve that goal, he creates carefully planned schemes that often put him on the wrong side of the law.
Moriarty and his brothers use their intelligence to challenge Britain’s unfair class system. Their plans often involve murder, deception, and manipulation, but they are not carried out without consequences. Every scheme forces Moriarty to deal with the people affected by his actions and the growing attention of those trying to stop him.
Sherlock Holmes eventually becomes the perfect opponent. Instead of relying on physical fights, the two constantly try to understand and outsmart each other. Their rivalry gives the series much of its tension, with each new confrontation feeling like a battle between two exceptionally clever minds.
Johan is not frightening because he is physically powerful. His intelligence and ability to manipulate others make him dangerous. Moriarty has a similar appeal because he is also highly intelligent and good at influencing people. However, his goals and personality are very different from Johan’s.
10. Serial Experiments Lain Takes a Different Look at Identity and Reality
If the psychological side of Monster interested you most, Serial Experiments Lain is worth trying. It is very different from Monster in its story and style. However, both series use their characters to explore identity, human nature, and the way people can change.
Serial Experiments Lain follows Lain Iwakura, a quiet and socially withdrawn girl whose life changes after she becomes involved with the Wired. As Lain gets deeper into the Wired, her understanding of herself and the world around her begins to change. She soon faces conflicts that make her question what is real and who she can trust.
Lain’s character development is one of the main reasons to watch the series. Her growing connection to the Wired changes how she sees herself and the people around her. As these changes continue, Lain faces a conflict that becomes harder for her to understand.
This sci-fi anime does not offer the same crime mystery or natural setting as Monster. Instead, it builds tension through its characters and their relationships. The questions surrounding identity and reality also make the story increasingly unsettling.
11. Ghost in the Shell: Stand Alone Complex Brings Investigation Into a Cyberpunk World
Ghost in the Shell takes place in a world filled with cybercrime, artificial intelligence, and political conspiracies. The story heavily focuses on Public Security Section 9. The team works together to investigate difficult cases and uncover the truth. With technology being part of everyday life, even simple cases can become complicated.
The investigations are one of the strongest parts of the series. Section 9 collects evidence, follows leads, and questions information instead of waiting for answers. The characters also have to deal with criminals, corporations, and government agencies.
Both anime take their investigations seriously. They give their characters enough time to understand the people and situations around them. The main difference is that Stand Alone Complex brings technology into the story. It also follows cybercrime and political conflicts.
The characters also have plenty of development throughout the story. Members of Section 9 bring different skills and personalities to their work, while their conflicts often reveal more about their beliefs and motivations. This gives the investigations a personal side.
12. The Perfect Insider Turns a Murder Mystery Into a Puzzle
If the mystery-solving side of Monster was what kept you watching, The Perfect Insider is worth adding to your list. It takes a more traditional detective approach. The story centers on a murder that seems almost impossible to solve. As the investigation moves forward, small clues slowly begin to reveal what really happened.
The biggest strength of The Perfect Insider is its focus on deduction. Instead of relying on constant action or emotional drama, the series asks viewers to pay attention to small details and follow the characters’ reasoning. Information that seems unimportant at first can become crucial as the investigation progresses.
That gives it a clear connection to Monster. Both anime trust their audiences to follow complicated mysteries rather than explaining everything immediately. The difference is that Monster expands its mystery across many characters, locations, and personal stories, while The Perfect Insider keeps its focus much tighter.
13. Rainbow Puts Survival and Human Relationships at the Center
What happens to people when they are forced to survive in a place where violence is part of everyday life? Rainbow: Nisha Rokubou no Shichinin explores that question through a group of young prisoners who form a strong bond while enduring harsh conditions in postwar Japan. Their friendship gives them the strength to face the conflicts, hardships, and struggles of life inside the detention center.
The conflict is not always about escaping or fighting back. Much of the story comes from the characters dealing with the damage caused by their environment and trying to hold on to their humanity. Their relationships develop slowly, and the reasons behind their actions are revealed as their individual pasts become clearer.
14. Ergo Proxy Brings Monster’s Philosophical Side Into Science Fiction
Ergo Proxy stands out because it combines psychological tension with a bleak science-fiction atmosphere. Its world feels cold, mysterious, and unsettling. This makes it very different from the natural setting of Monster.
The biggest difference is the genre. Monster focuses on crime and human psychology, while Ergo Proxy uses post-apocalyptic science fiction, androids, and futuristic technology to talk about similar questions. Its visual style is also much darker and more abstract, so it can take some time to get used to.
Despite those differences, the two anime share an important quality: neither gives viewers every answer immediately. Information is revealed slowly throughout the story. The audience has to pay attention to conversations, character behavior, and small details to understand what is really happening.
Both also follow questions about identity, free will, and human nature. Monster asks how an ordinary person can become something terrible. Ergo Proxy talks about similar ideas by questioning what it means to be human and whether identity can exist apart from the world around us.
15. Parasyte: The Maxim Questions What Makes Someone Human
Parasyte: The Maxim looks like a violent action-horror anime, but its strongest ideas are surprisingly thoughtful. Beneath the body horror and intense battles, the anime continually explores themes of morality, identity, and the value of human life.
One of its biggest strengths is how it challenges the usual idea of what a monster looks like. The parasites are easy to fear because they are physically different from humans, yet some of them can behave rationally and show their own understanding of life. At the same time, human characters are capable of cruelty, selfishness, and violence.
That makes Parasyte especially interesting for viewers who liked the darker questions in Monster. Johan’s story constantly raises questions about evil, human nature, and the reasons people become capable of terrible things. Parasyte talks about similar ideas from a completely different angle.
The two anime are very different in presentation. Monster is a psychological thriller with little emphasis on action, while Parasyte uses supernatural horror, graphic violence, and intense battles to talk about its themes. Its approach is much more direct and visually disturbing.
