Benimaru

Benimaru was originally the son of the chieftain of the Ogre village, designated as the next leader of his people.

His home was annihilated by the Orc Lord–led Orc army, leaving only a handful of survivors.

He later encounters Rimuru Tempest in the Great Jura Forest and initially mistakes him for the mastermind behind the attack on the Ogre village because of Rimuru’s mask.

After clearing the misunderstanding, he accepts Rimuru’s invitation, receives the name “Benimaru,” and evolves into a Kijin.

Benimaru is a tall, handsome man with deep crimson hair and eyes, and two jet-black horns, around 180 cm in height.

Over the story he evolves repeatedly, becoming first an Oni, then a Kijin-type higher spirit–demon hybrid, and ultimately a top-class holy-demonic spirit known as a Flame Dragon Ogre.

He is passionate, proud, and battle-loving, but also capable of self-restraint and calm judgment, especially compared with many of his comrades.

Rimuru places immense trust in him, assigning him command of armies and acknowledging him as a core pillar of Tempest’s leadership.

Name: Benimaru

Gender: Male

Former Race: Ogre (Oni)

Evolution Path: Ogre → Kijin → Youki (Oni) → Kishin (Flame Spirit Ogre) → highest-rank holy-demonic spirit Flame Dragon Ogre

Role/Occupation: Supreme military commander of the Jura Tempest Federation, samurai general, one of the Twelve Guardian Lords (Flare Lord)

Affiliation: Jura Tempest Federation (Tempest)

Height: About 180 cm

Hair: Crimson

Eyes: Crimson

Horns: Two black horns

Voice Actor (Japanese): Makoto Furukawa

Benimaru was once the young lord of the Ogres, raised to inherit the position of tribe leader.

He carries a strong sense of responsibility and justice, and he will confront anything he finds unforgivable head-on.

On the surface he is cool-headed and dignified, especially when acting as Tempest’s top military commander.

Underneath, he is very much an Oni: he enjoys combat, hates losing, and will happily accept a challenge to test his strength.

Compared to hotheads like Shion, his self-control is much better, and he has grown into a commander who can restrain his own battle lust for the sake of strategy.

He has a straightforward, honest nature and can be surprisingly pure-hearted, which makes him somewhat awkward with romance and marriage.

Benimaru is unexpectedly fond of sweets and likes snacks and desserts.

In contrast, he dislikes carrots, which becomes a running joke in spin-off works.

Although he is extremely popular and good-looking, he is oblivious to romantic signals.

Strong or direct advances tend to make him freeze up, and Souei teases him as being more timid and slow when it comes to love.

He admires his late father, who was devoted to one wife for his entire life.

Because of that, he struggles when both Momiji and Albis seek to marry him, feeling that taking multiple wives conflicts with his ideal image of a man.

Benimaru is depicted as a strikingly handsome young man with crimson hair and eyes and two jet-black horns.

His presence is intimidating yet charismatic, perfectly fitting his status as a warrior leader.

He has red vertical markings on both cheeks, which are actually scars from an accident in his childhood involving his younger sister Shuna.

Across different media adaptations, his hairstyle and facial details vary, often emphasizing either his “cool handsome” or “tough warrior” aspects.

In the original novel illustrations, manga, and anime, his hair has noticeable volume and his eyes are slightly narrow, giving him a strong, intimidating look.

In That Time I Got Reincarnated as a Slime: The Ways of the Monster Nation, he appears a bit younger and softer, with slightly less voluminous hair and larger eyes.

In the chibi spin-off series, he looks more like a rugged “manly” type than a pretty boy, with a slightly longer face and shorter hair.

Across all versions, his design consistently highlights his fiery nature and status as a frontline fighter.

Benimaru’s growth over the series is dramatic, turning him into one of the strongest combatants under Rimuru.

By the time of the main story’s later volumes, he stands as one of the “Three Peaks” of Rimuru’s forces.

Species Evolution:

Ogre → Kijin → Youki (Oni) → Kishin (Flame Spirit Ogre) → top-tier holy-demonic spirit Flame Dragon Ogre

Title: Flare Lord (one of the Twelve Guardian Lords)

Blessing: Blessing of Rimuru Tempest

Energy Points (EP):

Initially around 4,397,778 EP (+ 1,140,000 from his sword “Crimson Lotus”).

Later far exceeds 40,000,000 EP, and when augmented by the effect of “Prosperity” (Alta), approaches 100,000,000 EP.

Main Equipment:

A katana named “Crimson Lotus,” forged and repeatedly reforged by Kurobee until it attains mythic-level quality.

Magic:

Primarily flame-spirit magic and techniques that combine swordsmanship with flame and black fire.

Benimaru possesses both a powerful Unique Skill and, later, an Ultimate Skill, which together define his role as both commander and frontline destroyer.

His abilities specialize in reading and controlling flows of power and battle, and manipulating flame, light, and speed.

Unique Skill: Great Marshal

Benimaru’s Unique Skill Great Marshal grants him the ability to read and control the flow of power in himself, allies, and enemies.

It is a highly strategic ability that suits his role as supreme commander.

Key components include:

Thought Acceleration: Speeds up his thinking to process information and make decisions faster in battle.

Thought Domination: Coordinates mental links, allowing him to guide and command with overwhelming precision.

Predictive Calculation: Reads the flow of power and the state of the battlefield to predict outcomes with very high accuracy.

Army Encouragement: Enhances and coordinates the fighting spirit and performance of his troops.

Through this skill, Benimaru can minimize the risk of power going out of control and optimize his own output.

It also allows him to treat the battlefield like a board game, subtly steering both ally and enemy movements to his advantage.

Ultimate Skill: Lord of the Mirage Sun

After Rimuru’s evolution as a Demon Lord and subsequent ability fusion by Ciel, Benimaru acquires the Ultimate Skill Lord of the Mirage Sun.

This ability is based on the “Acceleration” authority of the scorching dragon Velgrind, fused with Benimaru’s existing talents.

Core features include:

Enhanced Thought Acceleration: Further boosts his mental processing speed to near-instantaneous tactical decisions.

Universal Perception: Grants wide-area, multi-layered perception across space, letting him “see” every detail of the battlefield.

Demon Lord’s Haki: A pressure that dominates the battlefield, suppressing enemies and inspiring allies.

Will Control: Fine control over his own will and the wills connected to him, stabilizing power and tactics.

Light and Heat Control: Allows him to freely manipulate light and heat, creating devastating flame and light-based attacks.

Space Control → Spacetime Manipulation: Initially provides spatial control, later upgraded to actual spacetime manipulation after instruction from Diablo.

Multi-layer Barriers: Generates multilayered barriers for both defense and battlefield control.

Battlefield Dominion: Inherits and amplifies the battlefield control aspect of Great Marshal, letting him dictate the flow of an entire war.

Additionally, Benimaru can apply this Ultimate Skill to the secret art “Mirage,” letting him semi-immaterialize his body.

Any attack that does not include Ultimate Skill–class factors simply passes through him, making him very hard to hit.

Benimaru is a frontline swordsman who combines incredible physical ability, high-level swordsmanship, and ultra-high-temperature flame and black fire.

He trains under Hakurou and eventually surpasses both Hakurou and the knight master Albert in pure sword skill.

General Fighting Style

He fights primarily with his katana “Crimson Lotus,” using sweeping, high-speed slashes imbued with flame and black fire.

His spatial awareness is exceptional, allowing him to read distance, timing, and trajectories almost perfectly.

Benimaru eventually becomes strong enough to cross swords on even footing with Diablo in a tournament, a feat achieved by very few.

As one of the three strongest under Rimuru, his individual combat power is comparable to or surpasses that of many awakened Demon Lords.

Hellflare

Hellflare is one of Benimaru’s most iconic techniques.

It creates a hemispherical barrier and fills it with black flames that incinerate everything within.

The technique is a composite of three abilities: black flame, heat manipulation, and area barrier.

Within its range, almost nothing survives—the attack is designed for large-scale annihilation.

Given his power, even among the surviving Ogres he stands out as unquestionably the strongest individual.

Hellflare exemplifies his role as a battlefield-wiping artillery swordsman.

Obscure Black Flame: Hundred Blossoms in Full Bloom

Obscure Black Flame: Hundred Blossoms in Full Bloom is a sword technique Benimaru develops by applying his Ultimate Skill.

He first demonstrates it in battle against the saint-class enemy Granit.

After gaining the Lord of the Mirage Sun, Benimaru can perceive views from his subordinates connected by the Soul Corridor with Rimuru.

Through this, he observes and learns Carrera’s techniques, then adapts them to his own style.

By combining light and heat control with Velgrind’s acceleration authority, he unleashes sword slashes at literally godlike speed.

Granit, despite being a saint-level fighter, is sliced into tiny pieces and burned to nothing in an instant without even reacting.

In the final battle against Jahil, Benimaru uses this technique again.

At that point, Jahil has absorbed Swim, Kakeashi, and Vega—who had devoured Zeranus—and has become an ultimate lifeform with EP in the hundreds of millions; even Shion, Ultima, Carrera, and Luminous Valentine together struggle against him.

Benimaru’s use of Obscure Black Flame: Hundred Blossoms in Full Bloom outright annihilates Jahil.

This shows how far beyond ordinary awakened Demon Lords Benimaru’s combat ability has grown.

Prominence Acceleration

Prominence Acceleration is a powerful art where Benimaru channels destructive red light and void black flame through his sword Crimson Lotus.

The red light burns all matter, while the black component is fueled by “Void Supply,” borrowing energy from the void.

The combined energy takes the form of a massive eastern-style dragon of black and red light.

Even as a momentary burst, the attack reaches an energy output in the tens of millions EP range.

It is strong enough to restrain a “berserk rampaging” Milim Nava, at least as a temporary stopper.

This technique demonstrates his capacity to output power on a scale relevant to the strongest beings in the setting.

Quartet Skill: Breakdown Nostalgia

Quartet Skill: Breakdown Nostalgia is a cooperative ultimate technique performed by Benimaru, Diablo, Zegion, and Dino.

All four are among the most powerful combatants in the world.

The combined attack produces a destructive force described as the greatest disaster since the birth of the universe.

If used on a planet’s surface, it could annihilate the planet and even engulf the entire solar system.

This technique illustrates the terrifying synergy between Rimuru’s top executives.

Benimaru, as one of the four participants, stands unquestionably among the absolute top-tier powerhouses.

Benimaru’s evolved form grants him extremely high-level defensive and resistance capabilities.

He is built to fight on the front lines of cosmic-level conflicts.

His known resistances include:

Physical Attack Immunity: Conventional physical damage is ineffective.

Natural Influence Immunity: Environmental and elemental effects such as extreme heat or cold do not affect him.

Status Ailment Immunity: He is immune to typical debuffs and abnormal conditions.

Mental Attack Resistance: He resists mental interference or control.

Holy-Demonic Attack Resistance: Attacks involving holy or demonic energy are greatly reduced in effectiveness.

These resistances, combined with his barriers and mirage-like intangibility, make him incredibly difficult to injure.

He can remain stable and functional even in apocalyptic-level battles.

Benimaru is not just a powerhouse; he is also Rimuru’s most trusted commander.

His Great Marshal and later Lord of the Mirage Sun skills are suited to large-scale warfare.

Positions and Commands

Rimuru appoints Benimaru as a samurai general and gives him full command authority over Tempest’s armies.

This includes controlling troop deployments, battle plans, and overall strategy in major conflicts.

He leads two major forces named by Rimuru:

The Red Flame Corps, composed of former child Ogres named by Rimuru.

The Green Numbers, a large goblin-based army.

After Tempest formally becomes a nation and undergoes military reorganization, Benimaru relinquishes command of the Green Numbers and First Corps to Gobta.

In exchange, he becomes the general of the Fourth Corps, built around the Red Numbers—elite troops with particularly strong ties to him.

On the battlefield, Benimaru uses his predictive abilities to read the flow of combat.

He is capable of making high-level decisions that consider both the individual fight and the overall war.

Growth as a Commander

Benimaru starts out as a passionate warrior who loves direct confrontation.

Through repeated campaigns and guidance from Rimuru, he learns to keep his temper in check and prioritize overall victory.

Strong enemies and the burden of responsibility force him to mature.

By the later stages of the story, he has become a level-headed tactical commander who can rein in his own battle lust for the greater good.

Rimuru often refers to him as his “right arm,” recognizing him as indispensable.

This mutual trust is a key pillar of Tempest’s stability and success.

Rimuru Tempest

Rimuru Tempest is Benimaru’s lord, savior, and closest superior.

After receiving his name and evolving, Benimaru voluntarily swears absolute loyalty to Rimuru.

Their relationship is not just master and servant but one of mutual trust and respect.

Rimuru relies on Benimaru as his general, while Benimaru respects Rimuru’s decisions and vision for Tempest.

In private, they often speak casually and on friendly terms.

Benimaru sometimes gets dragged into Rimuru’s sudden ideas, while Rimuru occasionally has his heart stop by Benimaru’s bold or seemingly reckless actions.

A notable moment is when Rimuru decides to become a Demon Lord to resurrect Shion.

Benimaru is ordered to be ready to kill Rimuru if he loses his mind and becomes a true monster after the ascension, which puts a heavy emotional burden on him.

In return, Benimaru proposes a password test to check Rimuru’s sanity: Rimuru must say, “Shion’s cooking tastes absolutely awful.”

Part of this is payback for being given the “correct Shion-cooking training” job and nearly dying for it, and part is hope that Shion will revive angry enough to react to the insult.

This plan backfires humorously when Rimuru, trying to dodge responsibility, mentions that the idea came from Benimaru in front of Shion.

Shion becomes furious, and Benimaru ends up forced to taste her cooking again—though fortunately, her new skills have improved it so it is no longer lethal.

Shuna

Shuna is Benimaru’s younger sister and his last remaining blood relative.

He loves her deeply and trusts her entirely with managing household and domestic affairs.

As she grows into an indispensable figure in Tempest, Benimaru finds he has almost no authority over her in daily life.

He and Shuna share a warm sibling relationship, but he is often powerless in front of her strong will and competence.

In The Ways of the Monster Nation, his inability to oppose his sister is a recurring comedic theme.

He even bonds with Gabiru over their shared trait of being unable to stand up to their little sisters.

Shion, Souei, Hakurou, Kurobee

Shion, Souei, Hakurou, and Kurobee are fellow survivors of the Ogre tribe slaughter.

Their shared tragedy and survival bind them closely together.

Shion and Souei are his childhood friends.

Souei is a close companion with whom Benimaru feels comfortable dropping all pretense and speaking frankly.

Hakurou is his sword master—an elderly swordsman who once knew Benimaru’s father.

Benimaru respects him deeply, and later surpasses him in pure swordsmanship, creating complex feelings and new connections.

Kurobee is the blacksmith who forged Benimaru’s beloved katana “Crimson Lotus.”

Through passion, effort, and repeated reforging for Benimaru’s sake, Kurobee raises Crimson Lotus to mythic-grade quality.

Father: Former Ogre Chieftain

Benimaru’s father was the previous chieftain of the Ogre tribe and a respected leader.

During the Orc Lord’s invasion, he sacrifices himself as a shield to ensure his children and retainers escape, dying along with many other Ogres.

Benimaru hears of his father’s earlier days from Hakurou, who describes him as a troublemaker in his youth, far from the dignified leader he later became.

He loved sweet dried persimmons that could be taken to the battlefield, a small but memorable detail.

For Benimaru, his father’s unwavering devotion to one wife becomes an ideal image of manhood.

This is one reason why taking multiple spouses—Momiji and Albis—initially troubles him so much.

Milim Nava

Milim Nava is one of the oldest and strongest Demon Lords and a close friend of Rimuru.

Benimaru and Milim share a somewhat trivial yet funny common trait: both dislike vegetables.

However, Milim will eat vegetables if they are cooked deliciously.

This leaves Benimaru in an awkward position, as Milim’s tolerance makes his own pickiness look worse.

In battle, Benimaru’s power rises to the level where he can temporarily restrain a rampaging Milim with Prominence Acceleration.

This underscores his growth into a fighter who can meaningfully interact with the strongest beings.

Diablo

Diablo is one of the Primordial Demons and serves as Rimuru’s second-in-command.

Both he and Benimaru secretly (and not-so-secretly) consider themselves Rimuru’s strongest subordinate.

In everyday interactions, they maintain polite distance and mutual respect.

Benimaru quietly views Diablo as a rival, while Diablo, confident in his own abilities, still holds genuine respect for Benimaru’s persistence and strength.

Diablo later teaches Benimaru how to apply his Ultimate Skill to actual spacetime manipulation.

This mentorship adds a layer of professional respect to their complicated rivalry.

Momiji

Momiji is the daughter of the long-nose tribe chieftain Kaede and the swordsman Hakurou.

She is officially Benimaru’s fiancée and later becomes his first wife.

At first, their arranged marriage is largely political, meant to strengthen ties between Tempest and the tengu village.

However, Momiji herself truly falls for Benimaru’s bravery and sense of justice.

She openly competes with Albis for Benimaru’s affection, but the two eventually grow close and start looking for a way both can be his wives.

Momiji ultimately becomes Benimaru’s primary wife (the first lady) and bears his children.

After the final battle, she gives birth to twins: a boy named Enju (Flame Tree) and a girl named Kureha (Autumn Leaf).

Both are born overwhelmingly strong, have no fixed lifespan, and possess the potential to become Demon Lords.

Albis

Albis is the leader of the Three Beastketeers and a serpent-type beastman serving under Demon Lord Karion.

During Clayman’s invasion of the Beast Kingdom Eurazania, Albis temporarily submits to Benimaru’s command.

Through seeing his leadership, tolerance, and strength firsthand, she gradually falls in love with him.

Albis is willing to accept being the second wife, so long as she can be with him.

She and Momiji initially clash repeatedly as romantic rivals, but each confrontation deepens their mutual understanding.

Eventually they decide to exploit a loophole in Tempest’s marriage system so that both can be married to Benimaru.

Albis becomes Benimaru’s second wife, and they conceive a child at almost the same time as Momiji.

After the final battle, she gives birth to a child named Kujya (Red Serpent), who has no defined gender, no fixed lifespan, and Demon Lord potential.

Other Allies and Interactions

Gobta: After the army reorganization, Benimaru entrusts the First Corps and Green Numbers to Gobta.

This shows Benimaru’s willingness to delegate and Rimuru’s broader strategy of elevating capable subordinates.

Karion: During diplomatic talks with the Beast Kingdom Eurazania, Benimaru impulsively challenges Demon Lord Karion to a test of strength and is beaten.

He returns to Rimuru happily reporting how strong Karion is, while Rimuru is left deeply worried.

Middray: When Benimaru encounters Middray, a priest-general from the Lost Dragon City forced to cooperate with Clayman, both are more than ready to duel one-on-one.

Since Benimaru is strong enough to kill monsters of Demon Lord–seed level in two hits, and Middray can spar with a True Demon Lord, their standoff terrifies their subordinates enough that they desperately stop them.

Benimaru’s pure, idealistic view of marriage makes him initially reluctant about marrying at all.

He does not want to betray his ideal of his father’s devotion to one woman.

However, Momiji and Albis approach marriage with serious determination and courage.

They demonstrate both political and personal commitment, as well as genuine affection for Benimaru.

Recognizing their resolve and the importance of ties between tribes, Benimaru finally accepts both of them as his wives.

This decision also aligns with Tempest’s broader diplomatic strategy and unites different races under one family.

With Momiji, he becomes the father of twins—Enju and Kureha—both born exceptionally powerful.

With Albis, he fathers Kujya, whose genderless nature and power symbolize a unique new step for their bloodlines.

These children embody the future of the re-established Ogre line, combined with the blood and power of tengu and beastmen.

Their existence also resolves Benimaru’s lingering regret about his destroyed tribe, allowing him to fully awaken as Flame Spirit Ogre and later Flame Dragon Ogre.

When Rimuru prepares for war against the Heavenly realm and begins awakening his executives into full Demon Lord–class beings, Benimaru initially cannot fully awaken.

The innate mission of the Ogre tribe—“revive and continue the tribe”—takes priority over his own evolution.

This natural restriction places his personal awakening on hold to protect the future of the Ogre bloodline.

Only once Momiji and Albis become pregnant, ensuring the Ogre line’s continuation, can Benimaru safely undergo full awakening.

After receiving a soul from Rimuru and resolving his lingering regrets as tribe leader, he awakens as Flame Spirit Ogre—a type of upper holy-demonic spirit.

Later, he reaches the even higher state of Flame Dragon Ogre, becoming one of Rimuru’s absolute strongest.

Despite all this power, Benimaru remains someone who reflects on his own failures.

For example, he admits that trying to “correct” Shion’s cooking was the first time in his life he truly felt “defeat,” before acquiring poison resistance.

In everyday life within Tempest, Benimaru is a reliable pillar everyone looks up to.

He balances his roles as general, noble leader, and family man.

In The Ways of the Monster Nation, battle scenes are rare, so Benimaru appears mostly in comedic, slice-of-life contexts.

He is shown dealing with domestic problems, enduring Shion’s cooking, and getting gently bullied by Shuna and others.

He is chosen as a “fire prevention campaign” character due to his flame powers.

He also uses his fire abilities for mundane tasks like melting snow—practical but somewhat overkill.

These depictions add humor and humanity to his otherwise fearsome, war-god-like image.

They highlight how, beneath the terrifying flames and god-speed sword techniques, Benimaru is a serious, somewhat stubborn, but ultimately kind-hearted man doing his best for his people.