Aku is the main antagonist in the cartoon Samurai Jack. He is also known as the "Master of Masters", "The Deliverer of Darkness", and the "Shogun of Sorrow". He was voiced by the late Makoto Iwamatsu.

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 bested him on numerous occasions, Aku merely transforms into a creature and escapes, usually calling out a taunt over his shoulder and escapes, a fact that he is entirely aware of and even makes a reference to in episode XLVIII.

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.

Main antagonist from The Powerpuff Girls Crossover 2. Ash is the King of Darkness, and he is Jack and King Hamtaro's enemies.



The episode The Birth of Evil reveals Aku's origins. Long ago in the vastness of space, a great, formless evil arose. Before it could do harm to the universe, it was set upon by three god-like figures known only as "The Deities". They are Odin, Ra, and Vishnu. During the battle, the deities' attack was fierce and the evil was all but destroyed save for a small fragment that was flung aside and it drifted for an unknown period of time before falling to Earth during the era of the dinosaurs (causing their extinction). It slowly grew and spread like poison over the course of the centuries, creating an ever-spreading forest of black spikes that devoured any who entered. Eventually the forest grew so large that the Samurai Lord of the Land (Jack's father) decided to kill the evil at its source. Armed with a magic oil given to him by Buddhist monks, the Lord and his cavalry rode into the heart of the forest, the Lord himself the only one to survive. Once at the black lake in the forest's center, the Samurai Lord doused an arrow into the oil he was given, shot it into the air, and into the black lake. Instead of destroying the evil, however; the magic arrow gave it humanoid form, sentience, and the ability to shape shift. Thus, the demon wizard Aku was born.

Aku easily defeated the Lord, trapped him on a giant, dead tree, and went on a rampage. The Deities, sensing the good in the Samurai Lord, summoned him to a secret place. Taking the good inside him, they forged an enchanted sword that is capable of harming Aku. Armed with the sword and a magical suit of armor, he plunged into battle against Aku. In the end, the Lord was victorious, but he was unable to destroy him, so he had to settle with trapping him inside the earth in the form of a tree. As he was sealed away, Aku vowed he would one day return. Shortly after, Jack's mother gave birth to him. Determined to learn from this and be prepared in the event Aku's vow came to pass, The Lord and his family decided that they needed a plan.


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 have gone since Jack left for his journey. His people, including his father, have become enslaved to dig up the resources of their land so Aku can begin to take over the world. After Jack completed his training, he came back and defeated all of Aku's demonic minions and freed the people of his land.

Jack then went to his tower to battle with Aku. After a vicious battle, Jack eventually overpowered Aku. However, before Jack could finish what his father started, a desperate Aku tore open a portal in time and flung him into the distant future, certain that he will be able to amass enough power to destroy him by then.

The Future

Many ages have passed since they last met. During that time, Aku slowly rose to power and enslaved most of the world, plundering its resources. But he still hungered for more power and opened his ports to the galaxy so he could pillage and dominate other worlds as well. Since then, his slow conquest of the galaxy has drawn aliens to the earth, making it topsy turvy.

Since Jack arrived in the future, Aku has kept a close eye on him and tries to destroy him many times.



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. 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.


Shapeshifting: Called the "Shape Shifting Master of Darkness" at the opening of each episode, 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. Aku's consciousness can exist even in a part of himself. He typically changes into animal forms that are threatening to fit certain situations, such as a scorpion or an octopus. He is however limited to his own colour scheme, no matter what form he takes it will always be black, red and green.

Known Forms he has taken

  • Bird (uses mostly to escape ) used lots of time
  • Scorpion :used in I and XXX also shown in opening titles
  • Gorrila:used in I
  • Billy Goat:used in I
  • Octopus:used in VIII and briefly seen in XXXVIII
  • Manta Ray:used in VIII
  • Spiked Tubeworm Forest:used in VIII
  • Spider:used in XXXVIII
  • Dark Tentacled being:used in I but also shown in begining opening titles
  • Dragon:used in XIII
  • Chinese Dragon:used in XXX
  • Preying Mantis:used in XXX
  • Mouse:used in XXX
  • Frog:used in XXXIV
  • Fish:used in XXXIV
  • Flying Dragon:used in XXXVIII
  • Dark Mass of shadow tentacles:used in XXX
  • Bat: used in XLVIII

Aku needs no food, drink, or air and is capable of interstellar travel. He also has the ability to spy on Jack through a large sphere he can summon at will in his tower.

As Aku is a great and powerful wizard, he possesses a wide knowledge of magic that varies from episode to episode as the series demands. His powers , as shown thus far in the series include:

  • Superhuman Strength: When Aku challenged Jack to a so called final match he was shown to have superhuman strength even in a somewhat human form.
  • Limited Invulnerability: Aku has shown the ability easily withstand weapons of any sort, such as simply absorbing arrows shot at him or not even being fazed after being hit by torpedoes as well as being capable of breathing underwater and existing in the depths of space, however he was shown to be vulnerable against mystic weapons and the weapons and artifacts of Deities and especially Jack's blade which was forged through the very essence of purity within Jack's father by the Deities Odin, Ra and Vishnu.
  • Fire Generation: Along with being capable of breathing fire Aku has also been shown creating it such as in one comical situation he had to re-ignite his eyebrows.
  • Time Travel: This was the very ability that Aku had used to send Jack into the future at the beginning of the series, though so far it has only been used once and was a one way portal forward in time.
  • Laser Eye Beams: Aku used this ability in numerous battles with Jack and he also used it to destroy the majority of Jack's Kingdom.
  • Teleportation: Aku uses this quite often to appear before those he has business with, such as the Imakandi.
  • Summoning Storms: Aku is capable of conjuring storms through will.
  • Magic Materialization: The ability to create objects out of thin air. He once used this ability to conjure gold, jewels, and treasure for the Imakandi.
  • Psychokinesis: Aku has shown the ability to move objects with his mind alone.
  • Sonic Scream: Aku was shown capable of producing a powerful scream that causes massive damage to the landscape.
  • Necromancy: Aku has been shown in one episode to be capable of animating countless dead bodies, and bending them to his will as they have neither mind nor soul.

A significant aspect in the series is that Aku is ageless and immortal. Aku's body is immune to nearly all forms of physical injury. If wounded, the wounds inflicted upon him will regenerate in moments. He can only be harmed and finally defeated by Jack's samurai sword. It is notable that Aku is also vulnerable to various magical and divine attacks (such as the powers and artifacts of gods).

Although Aku can transform into any form, his reflection will show his normal form, most noticeable when Aku turns into a hermit, and asks Jack to look for the god's artifacts. When Jack and Aku are in the swamp, Aku shows his normal form even when he is transformed into his hermit form. He will always have the same reflection, so he splashes the water, and uses the ripples to hide his reflection.


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

  • His shapeshifting is limited to his red, green, and black color scheme, also, his reflection will show his normal form, no matter what guise he takes.
  • He can be harmed by magical objects and attacks.
  • In one episode (XLIII), he appears to have somehow caught the flu.


Aku is evil incarnate, he embodies the very essence of an evil overlord. Cruel and domineering to all he might meet, it's obey or be obliterated with Aku. Arrogant and sadistic by default, he has been the ruler of most of the planet for thousands of years and does not take kindly to disobedience. Although he is merciless and inhumane, to say the least, he has enough of an understanding of humanity to successfully manipulate and control people when his powers aren't enough.

Despite this, he possesses a dry sense of humor and often jokes when in a good mood, frequently mocking Jack whenever he can and whatever he can. For instance, in the episode Jack Learns to Jump Good, Aku holds a time portal just out of Jack's reach.