Long ago in a distant land, I, Aku, the shape shifting master of darkness, unleashed an unspeakable evil.
But a foolish samurai warrior wielding a magic sword stepped forth to oppose me.
Before the final blow was struck, I tore open a portal in time, and flung him into the future where my evil is law.
Now the fool seeks to return to the past and undo the future that is Aku.

—Aku, Intro for Samurai Jack

Aku is the main antagonist of the series Samurai Jack. He is an evil, shapeshifting demonic entity that has taken over the world and ruled for countless eons. Throughout the series, he was voiced by the late Mako Iwamatsu in the original series but was replaced by Greg Baldwin in Season 5 following Mako's death in 2006.

Though he is capable of shifting form into virtually anything he wishes, his standard form is a roughly humanoid being with a black body, a green mouth, and a red beard extending from the bottom of his chin. He also tends to have six horns, four long and two short, extending from his head, and eyebrows made of red, flickering flame. In his standard form, he also tends not to have legs, with his body simply ending at the bottom with robe-like darkness that sometimes manifests as flames, and he also tends to be several stories tall. A deep droning noise is often heard around him when he appears.

Aku constantly antagonizes Jack, often attacking him when he is weak, and other times defending himself from Jack's own gambits. The two seem doomed never to defeat each other, for though Jack has beaten him on numerous occasions, Aku merely transforms into a creature and escapes, usually calling out a taunt over his shoulder, a fact that he is entirely aware of and even lampshades in "Episode XLVIII: Jack versus Aku".

While he's usually presented as a serious and threatening foe, Aku is also a source of comedy in the show, due to his outrageous design and sometimes wise-guy behavior, supported by Mako's over the top voice-acting.

Aku means "Evil" in Japanese. It is written as "悪" in Kanji. The kanji can also be pronounced as "Waru".



Long ago in the vastness of space, a great, formless, mindless entity of evil arose. Before it could do harm to the universe, it was set upon by the three prime deities of the Aesir, Egyptian, and Hindu mythologies: Odin the All-father, Ra the Sun God, and Vishnu, the Supreme God and Soul. The three deities fought a fierce battle against the black mass, burning the entity almost completely out of existence with their divine power. However, during the battle, one small fragment of the entity was incidentally cut from the whole by Odin and did not burn away. Unnoticed by the three deities, this seemingly small fragment floated away from the site of the battle and drifted through space for an untold amount of time, until it eventually, and violently, crashed on Earth during the Cretaceous period of the Mesozoic era. It is implied that the fragment of the black mass was the very object that caused the extinction of the dinosaurs (although the crash occurred in prehistoric Japan as opposed to the Yucatán peninsula by a massive asteroid even though it is possible that both impacts occurred around the same time 65.5 million years ago). Over eons, the fragment evolved into an ever growing ominous forest of black tree-like spikes, surrounding a tar-like pit at its center that devoured any living thing that dared enter. Eventually the forest grew so large that The Emperor (Jack's father) decided to kill the evil at its source. Armed with a poison elixir given to him by a Buddhist monk, the Emperor and his cavalry rode into the heart of the forest. But as they rode, the forest began to kill his men, leaving the Emperor himself as the only survivor. Once he arrived at the black lake in the forest's center, the Samurai Lord doused an arrow into the elixir he was given and fired it into the black lake, believing that it would destroy the evil forest. Unexpectedly, the poison arrow's magic had the unforeseen effect of galvanizing the evil mass into a humanoid form, giving it intelligence, sentience, and shape-shifting abilities. The evil proclaimed it's name to be Aku, and thanked the Emperor for inadvertently helping him. The Emperor attacked Aku, but, with nothing more than his mundane, mortal weapons, he could inflict no harm upon the demon. Aku easily defeated the Emperor, and trapped him to the side of a tree so that he could watch as Aku destroyed his home and killed his people. However, the Deities, sensing the good in the Samurai Lord, summoned him to them. Taking the good inside him, they used avatar bodies to create an enchanted sword that was capable of harming Aku. Armed with the sword and a magical suit of armor, the Emperor plunged into battle against Aku. In the end, the Emperor was victorious, but he was unable to destroy the demon, and so instead sealed him in the devastated wasteland in the form of a jagged black tree. As he was sealed away, Aku vowed he would one day return. During the battle, the Emperor's wife gave birth to a son. Determined to learn from the catastrophe, and aware that Aku would indeed one day return, the Emperor and his family hatched a plan, and orchestrated the events that would set Jack on his eventual years of training.


Ten years later, during a solar eclipse, the tree form that Aku was imprisoned in dissolved and Aku was released. In a castle, Jack was a young child and his father was telling him how he defeated Aku. After the story was done, Jack was left alone, playing with a toy sword. Suddenly, the castle was covered in Aku's shadow. Aku unleashed a vicious attack on the city. Jack's father attempted to get the sword, but Aku captured him before he could reach it. The Lord told his wife it was time to enact the plan they had prepared. Following the plan, Jack's mother escaped with him and the sword. Jack then started on his journey to prepare both physically and mentally for his confrontation against Aku.

Many years later, a formidably trained Jack returned to find his land devastated and his people, including his father, enslaved and horribly suffering, forced to harvest the rich resources of their land for Aku to increase his powers and spread his evil across the entire planet. Filled with righteous wrath, Jack quickly slew Aku's minions and went to Aku's palace to slay him. After a vicious battle, Jack eventually overpowered Aku. However, before Jack could finish him off, a desperate Aku tore open a portal in time and flung him into the distant future, a future in which Aku was certain that his evil would be spread out all over the world.

The Future

Unknown centuries passed before Jack reappeared into the world. During that time, Aku managed to terrorize and subjugate the majority of the entire world, making himself the undisputed ruler of Earth. Although he began with demonic servants to carry out his will, he later became enamored with mechanical servants due to the fact his demonic minion doesn't carry his task fast enough, and recruited mad scientists to make the X-Model. All but one were eventually destroyed before the next generation of Aku's army were developed: the Beetle Drones. Successors to the X-Models, the beetle drones became the model for a series of insect-themed minions that served Aku well into the height of his power, and were his standard henchmen.

Hungry for more power, Aku established the Earth as a space-faring world, opening his ports to surrounding worlds in order to plunder and conquer worlds beyond as well. The influx of aliens, ranging from enslaved species to rough immigrants, have made the Earth a hodge-podge of a dystopian society primarily run by tyrants and gangs. The few bastions of peace and hope typically remain out of Aku's wide field of vision.

Since Jack arrived in the future, Aku habitually watches his progress through the world, and takes any and every opportunity to destroy the samurai, whether through unleashing his minion armies, hiring bounty hunters, using power objects, clever traps, trickery and deceit, and other methods in an unending struggle.

Despite being highly feared, hated and despised by almost all sentient beings in the world and the universe, some people worship him like a divine figure. The prime example is the Cult of Aku.

50 Years in the Future

Fifty years after Samurai Jack arrived in the future, Aku managed to destroy almost all of the world's time portals. With Jack's ability to travel back to his own time seemingly eliminated, Aku decided to stop confronting Jack and simply wait for the samurai to die of old age. However, it later became apparent that Jack's initial time-travelling had halted his natural aging process, leaving him forever at the age that he was when he first went through the time portal. This discovery scuttled Aku's plan and left him at somewhat of a loss as to what to do about his now timeless foe.



Aku reveals himself.

Ikra was one of Aku's aliases, just one of several forms which Aku assumed in order to travel closely with Jack. Using his shifting abilities Aku changed himself to the appearance of a young woman with green skin, black hair and a black dress. She/He travelled with Jack across the desert, battling many dangers together. Under the guise of Ikra, Aku and Jack had formed a close bond (at one point Ikra even saves him from drowning in quicksand). Ikra told Jack that her father, like Jack's, had fought with Aku and having lost been forced to spend eternity trapped in a ring of fire and that she was on a quest to find a magical jewel in the desert which was powerful enough to free her father. When Aku reveals himself as having been Ikra the whole time he mocks Jack for having believed the story about her father.

The Hermit

The Hermit was another one of Aku's aliases, just one of several forms which Aku assumed in order to travel closely with Jack. Using his shapeshifting abilities Aku changed himself to the appearance of an old cranky hermit with green skin, white hair and a black robe. He travelled with Jack to find the Gems of Cronus, looking for one gem to the other, in order to resurrect Cronus. Unlike with Ikra, Jack saw through the deception and was ultimately able to turn the tables on Aku. In the ensuing battle Jack defeated and heavily injured Aku, forcing him to retreat.


An incarnation of primordial evil, Aku is a formless entity, wields vast magical powers, and is one of the most powerful beings in the series, with only few beings capable of fighting him.

  • Immortality: A significant aspect in the series is that Aku is ageless and immortal. He requires no sustenance, and cannot be harmed by earthly methods. Only the power of mystical weapons like Jack's sword, or divine entities are capable of hurting him and bring about his destruction.
  • Shapeshifting: Aku can change into virtually any form he desires, from a giant dragon to a small insect, or even a beautiful woman. He can also change his size, liquefy himself, stretch, and expand his body. He can also replicate into clones of himself to be in numerous places at once, with his mind inhabiting numerous bodies. Fifty years into the future, he even forms a perfect doppelganger of himself to perform therapy with himself. He typically changes into animal forms during battle, such as a scorpion or an octopus, adapting to the situation. On one occasion, he also transformed into a huge, amorphous mass of darkness that greatly resembled the evil entity he had previously once been/spawned from, and could alter parts of himself at will.
    • Supernatural Physical Ability: Aku can alter his physical capabilities to virtually any level he needs or wants due to his magical shape-shifting abilities, and has manifested superhuman strength, speed, endurance, and senses. No parameters or upper limits have been established regarding these capabilities. 
    • Regeneration: While Aku is completely resistant to most forms of attack, he is not invulnerable; items such as Jack's sword or magics such as divine energy can damage the substance from which he is made. However, Aku is able to regenerate to a large degree even against attacks such as these; the magic or item will create large, burning holes or gashes in him that he can close back up with effort. However, his ability to regenerate in these situations is limited. In many of his confrontations with Jack, damage caused by the sword whittles away at his overall mass and ability to regenerate in the short term, until it tends to leave him as a very small animal of some sort, such as a frog or a mouse, at which point further attacks would presumably either seal him away as Jack's father did, or kill him as Jack intends to do. However, given time, he will eventually restore himself.
  • Dark Magical Abilities: Aku, being a demonic manifestation of a primordial evil, can naturally tap into various dark magical energies to cast spells, and perform great supernatural feats. There appears to be little to no limit to the scope of his abilities. The powers he has demonstrated so far are:
    • Laser Eye Beams: Aku's most used attack. He has used this ability in numerous battles with Jack, and he also used it to destroy the majority of his past kingdom. Aku can also teleport beings to places of his choosing through this power.
    • Scrying: Using mystical forces in his lair, Aku can create images on the walls to spy upon Jack, not to mention other enemies and events.
    • Time Portal Creation: This was the very ability that Aku used to send Jack into the future at the beginning. It was only used once and was a one way portal forward in time.
    • Teleportation: Aku uses this often for quick escapes, and to appear before those he has business with, such as the Imakandi.
    • Elemental Control: He can magically project and control the very elements of the physical world, like breathing streams of fire, raising the earth itself, conjuring thunderstorms at will, or emitting waves of sonic force from himself. By combining fire breath with his eye lasers, Aku projects beams of electricity.
    • Telekinesis: He has shown the ability to manipulate objects by his will.
    • Object Materialization: The ability to create objects and materials out of nothing. He once used this ability to conjure treasures in the presence of the Imakandi.
    • Necromancy: Aku has been shown in one episode to be capable of animating countless dead bodies, and bending them to his will.
    • Premonitions: On one occasion, Aku has been shown to be able to receive premonitions regarding his future through his dreams, which he can then act upon.
    • Possession/Infection: Aku can use small portions of himself to infect others with his evil. The only time this has been seen was when he incidentally spat up a tiny portion of himself at Jack, which, over the course of a day or so, proceeded to possess Jack, giving him the appearance and personality of Aku. On a related note, he can also use portions of himself to power machinery, as he demonstrated by doing so with the Ultra-Robots.
    • Interstellar Travel: Aku is capable of interstellar travel at the speed of light.
  • Combat Skills: Despite never having been shown to have trained at all in any form of martial art, Aku is a very skilled practitioner of hand-to-hand combat. Though not any sort of match for Jack, he was at least capable of defending himself reasonably well against Jack during their duel, while limiting himself to using only human capabilities. He is also shown to be a fairly skilled swordsman, as, on one occasion where he stole Jack's sword, he was able to force Jack (who was armed with a sword and shield) into a defensive posture during a bout of swordplay. However, it should be noted on that occasion that Aku was not limited in the scope of the powers he could employ.

Known forms he has taken

  • Bird: (he uses this form mostly to escape) used lots of times
  • Scorpion: used in I and XXX also shown in opening titles
  • Gorilla: used in I
  • Billy Goat: used in I
  • Squid: used in VIII and briefly seen in XXXVIII
  • Manta Ray: used in IX
  • Spiked Tubeworm : used in IX
  • Spider: used in XXXVIII
  • Kraken: used in I but also shown in beginning opening titles
  • Cobra: used in XII
  • Dragon: used in XIII
  • Chinese Dragon: used in XXX
  • Praying Mantis: used in XXX
  • Mouse: used in XXX
  • Frog: used in XXXIV
  • Fish: used in XXXIV
  • Flying Dragon: used in XXXVIII
  • Army: used in XXXVIII
  • Dark Mass of Shadow tentacles: used in XXX
  • Human: used in XLVIII
  • Amorphous Mass of Darkness: used in XXX
  • Therapist doppelgänger: used in XCIII


Despite his powerful abilities, Aku has a few weaknesses. These include:

  • Color Scheme: Aku's shape-shifting is limited to his color scheme and will remain red, black, and usually green (though not always) no matter what form he takes. While not particularly problematic with regard to combat, this can make disguising himself somewhat difficult (though he has still fooled Jack numerous times with his disguises, as Jack tends not to notice Aku's color scheme issues and, when he does see through Aku's disguises, it is because of Aku's personality rather than his colors).
  • Reflection: Aku's own reflection will reveal his normal form no matter what he has shifted to look like.
  • Magic: Though Aku cannot be harmed by normal weapons and attacks, he can only be harmed, defeated and vanquished by Jack's sword and other divine or mystical forces. For example, the Goddess of Water and her 3 elemental servants were able to harm and defeat Aku with very little effort, although not to the same degree as three 3 gods Odin, Ra and Vishnu. Since Aku was a fragment of the greatest manifestation of evil, he can be destroyed by the strength and purity of a human's (and likely any other living creature) spirit, as stated by Vishnu. Jack's katana is virtually the only item which can cause Aku damage that he cannot instantly regenerate from. For this reason, Aku is reluctant to confront Jack head-on.
  • Illness: In one episode (XLIII), Aku appeared to suffer from flu-like symptoms, exposing an apparent lack of immunity to diseases. However, it is unknown how he managed to contract whatever illness he was suffering from.
  • Vulnerability to Divinity: Powerful deities like Ra, Vishnu, Odin, the Goddess of Water and her elemental servants are able to overpower and vanquish him.


Aku is evil incarnate; he embodies the very essence of an evil overlord. Cruel and domineering to all he meets, it's obey or be obliterated with Aku. Arrogant and sadistic by default, he has ruled the planet for thousands of years and does not take kindly to disobedience. He is merciless and inhumane to say the least, but has enough of an understanding of humanity to manipulate their feelings to his advantage.

Aku is as intelligent as he is powerful, and his cunning knows little end, from taking the form of a woman to trick Jack or manipulating various races into serving him. He is also dishonest and has no shame or remorse, and he routinely goes back on his word either to serve himself or simply for amusement.

Despite this, he possesses a dry sense of humor and often jokes when in a good mood, mocking Jack whenever he can and however he can. For instance, in one episode Aku holds a time portal just out of Jack's reach as Jack jumps for it. He is also rather "genre savvy", and will occasionally lean on the fourth wall or lampshade either his own villainous tendencies or various cliche situations. He is also a frequent source of comic relief in the show, due, in prime, to his reactions to the things around him.

Aku seems to have soft spot for children. This can be seen in Aku's Fairy Tales where he attempted to make children admire him by telling them tales that depict himself as a hero and Jack is a villain. Unfortunately for him, the children weren't impressed hearing his increasingly ludicrous tales, causing him to vanish in rage after roaring "the end".

After 50 years of battling Jack, Aku's personality seems to be largely unchanged, though he had become perhaps slightly more mellow. He ostensibly no longer cares whether or not Jack lives or dies, but despite the nonchalance he displays toward his minions regarding the subject, he is actually deeply disturbed by the fact that Jack appears to now be ageless as a result of his initial time-travel.

Apperances in Other Media

  • Aku was featured frequently in Cartoon Network commercial bumpers from 2001 to 2007.
  • Aku makes a brief appearance in the intro to the short-lived programming block, Friday Nights. He can be seen early on standing in the city, rivaling a few skyscrapers in height.
  • Aku appears as an unlockable Nano character in the Cartoon Network MMO, FusionFall. This is his first speaking role since the passing of his previous voice actor, Mako Iwamatsu. He was voiced by Greg Baldwin.
  • He appears in both the handheld and console versions of Cartoon Network Punchtime Explosion as a boss character. He is a playable fighter in the console version as well. He was voiced by Fred Tatasciore.
  • Aku made multiple background appearances during Cartoon Network's 20th Anniversary celebration.


  • "Who dares to summon the Master of Masters, the Deliverer of Darkness, the Shogun of Sorrow, Aku!?"
  • "That sword. I remember that blade. I recognized your blood. You are the son of the fool who imprisoned me those many years ago. No matter, neither he or the sword has the power to slay me forever, and neither do you!"
  • "Do not worry, Samurai, you will see me again. But next time, you shall not be so fortunate."
  • "I don't feel good."
  • "I seek to foil the samurai! To destroy his dream of returning home and to destroy all who stand in my way!"
  • "Extra thick!"
  • "Useless Bounty Hunters!"
  • "Yes. It is I, Samurai Jack. How incredibly observant you are".
  • "I'll be back, Samurai. You'll see. HAHAHAHAHA!!! See what I mean?"
  • "Tsk, tsk, tsk. Coulda, shoulda, woulda. It's all part of life's sweet sorrow. You're so lucky, samurai. Most of us get to live with our mistakes, but you get to die by yours!"
  • "But he hasn't even aged. I mean like it all. He just grew that stupid beard and it looks like he'll be here forever. I... I just don't know if I can handle that."


  • In the early episodes of the show, the red color of Aku's flame extended to a red outline around his eyes. This outline was quickly dropped from his design. In season 5, the green lining between his eyes has been removed from his design.
    • Similarly, his eye beams were initially yellow in early seasons, but became white from season 3 onwards.
  • Aku was parodied several times in Duck Dodgers, a Warner Brothers-produced cartoon starring Daffy Duck that ran alongside Samurai Jack's original run. In the show, Mako Iwamatsu voiced "Happy Cat", a loud and obnoxious cartoon cat with a large amount of merchandise showcased throughout the show. The Happy Cat alarm clock used by Dodgers featured Mako's voice, using Aku's distinct laugh and voice. In the episode "Samurai Quack", a parody of Samurai Jack, Aku was recreated as "Achoo", a combination of him and the Happy Cat character.
  • Many of Aku's sudden movements are accompanied by the sounds of creaking wood. This is presumably because of his body having been created from the black trees he originally took the form of.
  • Aku was voiced by the late Mako Iwamatsu for the show's original run. He was known for portaying such characters as Splinter from the 2007 Teenage Mutant Ninja Turtles film, and Iroh from Avatar: The Last Airbender.
    • As Mako passed away in 2006, any speaking roles by Aku following would have been taken up by other actors. In FusionFall, he was voiced by Greg Baldwin (who, incidentally was also the one to replace Mako as the voice of Iroh in Avatar), and he was voiced by Fred Tatasciore in Punchtime Explosion and Punchtime Explosion XL.
    • Interestingly, a storyboard sneak peek of Season 5 had Genndy himself attempting to imitate Aku's iconic voice. However, as it was an animatic, it's not uncommon for the person pitching the scene to do all the voices themself as placeholders.
      • Later on, it was confirmed that Greg Baldwin would voice Aku in Season 5.


Main article: Aku/Gallery
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