Kamen Rider Build, which aired from September 2017 to August 2018, stands as the 19th entry in the Heisei era of the Kamen Rider franchise. It is a series defined by its high-concept science fiction, intricate geopolitical drama, and some of the most profound character writing in the history of the medium. Set in a version of Japan divided by a massive, mysterious barrier known as the Skywall, the story follows Sento Kiryu—a genius physicist with amnesia—as he uses the "Build Driver" to fight monstrous creatures called Smash while unraveling a conspiracy that spans planets.

The brilliance of Kamen Rider Build lies not just in its flashy transformation sequences or collectible gadgets, but in its unwavering commitment to exploring the ethics of scientific discovery and the devastating cost of war. It is a narrative where science is both the source of destruction and the only path to salvation.

The Skywall Incident and the Fractured Japan

The foundation of the series is rooted in a cataclysmic event known as the Skywall Tragedy. Ten years before the start of the story, a Japanese expedition to Mars recovered a mysterious artifact called the Pandora Box. During the celebration of their return, an incident caused the box to activate, unleashing a massive energy pulse that manifested the Skywall—a literal and metaphorical wall that split Japan into three warring territories:

  1. Touto (Eastern Capital): A pacifist state that possesses the Pandora Box but aims for peaceful resolution.
  2. Hokuto (Northern Capital): A territory suffering from social collapse and poverty, eventually turning to military aggression to survive.
  3. Seito (Western Capital): A technocratic and militaristic state seeking to unify Japan under its own authority through advanced weaponry.

This setting transforms the typical "hero vs. monster" formula into a complex war drama. The "Smash" monsters are not mystical demons but the results of illicit human experimentation using Nebula Gas—a substance derived from the Pandora Box. By grounding the conflict in state-level politics and biological engineering, Kamen Rider Build elevates the stakes from local safety to national survival.

Sento Kiryu: The Architect of Love and Peace

The protagonist, Sento Kiryu, is a self-proclaimed "genius physicist." Unlike many previous Kamen Riders who are chosen by destiny, Sento builds his own destiny through engineering. His arsenal, including the Build Driver and the Fullbottles, are tools he designed or refined to neutralize the Smash threat.

However, Sento’s character is defined by a haunting paradox. He suffers from total amnesia, knowing only that he was experimented on by the shadowy organization Faust. As the series progresses, Sento discovers his true identity as Takumi Katsuragi, the very scientist who pioneered the Nebula Gas experiments that led to the creation of the Smash and the weaponization of the Kamen Rider system.

This revelation forces Sento to confront the "sins of science." He is a hero fighting for "love and peace," yet his very existence and the powers he uses are rooted in human suffering. His struggle to maintain his morality while utilizing weapons of war is the emotional anchor of the series. The show asks a difficult question: Can the inventions of a "Devil's Scientist" ever be used for the greater good?

The Best Match: The Chemistry of Sento and Ryuga

A critical component of Kamen Rider Build's success is the relationship between Sento Kiryu and Ryuga Banjo. Ryuga, a former professional fighter wrongfully accused of murder, serves as the perfect foil to Sento’s intellectualism. While Sento analyzes the "winning formula" for every battle, Ryuga acts on instinct and raw emotion.

Their partnership is referred to as the "Best Match," a term taken from the Build Driver’s mechanism where two specific Fullbottles (like Rabbit and Tank) create a perfectly balanced combat form. Their dynamic evolves from reluctant allies to brothers-in-arms who constantly challenge and support one another:

  • Complementary Strengths: Sento provides the logic and tools, while Ryuga provides the heart and the "will to never lose."
  • Shared Trauma: Both are victims of the Pandora Box incident and the organization Faust, creating a bond forged in shared suffering and a mutual desire for justice.
  • The Power of Growth: Ryuga’s transformation into Kamen Rider Cross-Z represents one of the strongest character arcs in the franchise, as he moves from a selfish fugitive to a man willing to sacrifice his humanity to save the world.

The Motifs of Science and the Winning Formula

The "Science" motif is integrated into every aspect of Build’s combat and aesthetics. The Build Driver functions like a centrifuge, shaking the Fullbottles to extract their essence. When Sento transforms, he is surrounded by blueprints and chemical formulas. His catchphrase—"Now, shall we begin the experiment?"—frames each battle as a hypothesis testing session.

Fullbottles and Experimental Logic

The Fullbottle system is categorized into two types:

  • Organic (Biological): Essence of living things like Rabbits, Lions, or Gorillas.
  • Inorganic (Mechanical): Essence of man-made objects like Tanks, Gatling guns, or Vacuums.

A "Best Match" occurs when an organic and an inorganic bottle complement each other’s properties. For example, the "RabbitTank" form combines the agility and speed of a rabbit with the durability and firepower of a tank. This mechanic reflects the scientific method—finding the optimal combination of variables to achieve a specific result.

The Danger of the Hazard Level

The series introduces the concept of the "Hazard Level," a numerical measurement of a person's compatibility with Nebula Gas. As a Rider fights, their Hazard Level increases, granting them more power but also making them more susceptible to losing their humanity. This serves as a brilliant metaphor for the escalating arms race. The introduction of the "Hazard Form"—a pitch-black, berserk transformation—shows the terrifying consequences of pushing scientific boundaries too far. In one of the most chilling episodes of the series, Sento loses control in this form and commits an act of violence that he can never take back, marking a dark turning point in the narrative.

The Antagonists: Political Schemes and Extraterrestrial Malice

Kamen Rider Build features a multi-layered hierarchy of villains that keeps the plot unpredictable.

Gentoku Himuro (Kamen Rider Rogue)

Initially the Prime Minister's son and the leader of Faust, Gentoku is driven by a misguided sense of nationalism. He believes that for Touto to survive the coming war, it must possess the strongest military force. His transformation into Night Rogue and later Kamen Rider Rogue highlights his fall from grace and his eventual, painful path toward redemption. His character arc explores the theme of how fear and the desire for power can corrupt even those with supposedly patriotic intentions.

Evolto (Kamen Rider Evol)

The primary antagonist, Evolto, is an alien entity from the Blood Race responsible for the destruction of Mars. Disguised for years as Soichi Isurugi, the kind cafe owner who took Sento in, Evolto is a master manipulator. He doesn't just want to destroy the Earth; he wants to play with its inhabitants, treating the war between the three capitals as a game.

Evolto is often cited as one of the greatest villains in tokusatsu history because of his charisma and his overwhelming power. He is the ultimate antithesis to Sento: while Sento uses science to build and protect, Evolto uses the Pandora Box's energy to consume and destroy. His presence raises the stakes from a local civil war to a cosmic threat.

The Three Capitals War: A Dystopian Mirror

As the series enters its second act, the tension between Touto, Hokuto, and Seito erupts into a full-scale war. The show does not shy away from the grim realities of conflict. We see the displacement of civilians, the deployment of "Hard Smash" soldiers who have sacrificed their lives for their respective states, and the cold-blooded calculations of government leaders.

The "Hokuto Three Crows"—a trio of soldiers who serve Kazumi Sawatari (Kamen Rider Grease)—are particularly tragic. They represent the human cost of the Skywall; men who volunteered for experimentation to provide for their families and support their leader. Their eventual deaths serve as a brutal reminder to Sento and the audience that in war, there are no true winners.

Kazumi Sawatari himself brings a different perspective to the Rider team. As a farmer turned soldier from Hokuto, his loyalty is to his people rather than an abstract ideology. His "burning passion" provides a stark contrast to Sento’s cool logic, further enriching the show’s exploration of what it means to be a hero.

Production Excellence: The Vision of Shogo Muto

One of the reasons Kamen Rider Build feels so cohesive and serialized compared to other entries is its production structure. Head writer Shogo Muto wrote all 49 episodes of the series, a rare feat in modern tokusatsu. This solo writing effort ensured that the complex mysteries—such as the truth behind the Pandora Box, Sento's past, and Evolto’s true form—were paced perfectly throughout the year.

The series avoids the "monster of the week" filler that plagues many long-running shows. Every episode contributes to the overarching plot, with twists that are foreshadowed dozens of episodes in advance. The production team, led by producer Takahito Omori, successfully balanced the commercial requirement of selling toys (the various bottles and drivers) with a dark, mature narrative that respected the audience's intelligence.

The Ethics of the Pandora Box

The Pandora Box serves as a central MacGuffin that mirrors nuclear energy or AI in the real world. It contains enough energy to power the world forever or destroy it in an instant. The characters' reactions to the box define their moral compass:

  • The Government Leaders see it as a deterrent or a weapon to ensure dominance.
  • Faust sees it as a means to evolve the human race through force.
  • Sento sees it as a burden that must be contained or purified.

The resolution of the series, involving the merging of parallel worlds to create a new reality without the Skywall, is a bittersweet ending. It reinforces the idea that while science can fix the problems it creates, the scars of the past—and the memories of those lost—remain.

Why You Should Watch Kamen Rider Build Today

Even years after its conclusion, Kamen Rider Build remains a high-water mark for the franchise. It succeeds because it treats its audience with maturity. It understands that children can grasp complex themes of war and sacrifice, and it provides adults with a gripping sci-fi thriller that rivals prestige television.

The show offers:

  1. A tight, mystery-driven plot that keeps you guessing until the very end.
  2. Unforgettable characters with genuine chemistry and growth.
  3. High-stakes action that carries emotional weight.
  4. A thoughtful exploration of science as a tool for both good and evil.

For anyone looking to dive into the world of Japanese tokusatsu, or even for seasoned fans looking for a rewatch, Build offers a "winning formula" that is hard to beat.

Conclusion

Kamen Rider Build is a masterclass in serialized storytelling. By combining a dystopian political landscape with the personal journey of an amnesiac scientist, it creates a narrative that is both epic in scope and intimate in emotion. It reminds us that science is not just about formulas and experiments; it is about the heart of the person who wields it. Whether it is the frantic shaking of a Fullbottle or the tragic sacrifice of a comrade, Build leaves an indelible mark on its viewers, proving that even in a world divided by walls, the pursuit of "love and peace" is a battle worth fighting.

FAQ

What are the "Best Matches" in Kamen Rider Build?

A "Best Match" occurs when Sento uses two Fullbottles that have a special chemical synergy, resulting in a unique transformation sound and enhanced combat abilities. The most famous is RabbitTank, but other notable matches include GorillaMond (Gorilla and Diamond), HawkGatling (Hawk and Gatling), and NinninComic (Ninja and Comic).

How many episodes are in Kamen Rider Build?

The main television series consists of 49 episodes. However, the story continues through several movies, including Kamen Rider Build the Movie: Be the One and the V-Cinext specials like Build NEW WORLD: Kamen Rider Cross-Z and Build NEW WORLD: Kamen Rider Grease.

Who is the strongest Rider in the series?

While power levels shift, Kamen Rider Evol (Evolto) in his Black Hole Form is widely considered the most powerful for much of the series. However, Sento’s final form, Kamen Rider Build Genius Form, allows him to neutralize Nebula Gas and manipulate the powers of all 60 Fullbottles, making him the ultimate counter to Evolto.

Is Kamen Rider Build connected to other Kamen Rider series?

As part of the Heisei era, Build exists in its own universe but crosses over with other Riders in the Heisei Generations movies. The series finale actually plays a significant role in explaining how the Build universe connects to the broader Kamen Rider multiverse during the transition to Kamen Rider Zi-O.

What is the meaning of the name "Build"?

The name "Build" (ビルド) refers to Sento's nature as a creator and architect. He "builds" his own gadgets, his own identity, and ultimately, a new world where people can live in peace. It also plays on the word "Building" in the context of the Skywall and the divided nation.