As stated, Ninetails is a nine-tailed kitsune with golden coloured fur. Each of its long tails ends with a brush-like tip dipped in red ink, and hoods with masks just below the brushes. The central tail, which houses Ninetails' true form, also has a necklace of red beads around the mask. Ninetails wears a white mask with red markings, as a mockery of Amaterasu's divine appearance. However, when all of Ninetails' tails are destroyed but the central one, then the demonic kitsune is revealed to be a mere old and beaten up fox with a single tail and a lost eye (which was previously covered by its mask).
In battle, Ninetails uses Ninestrike, the seemingly dark copy of Seven Strike, and other fighting techniques that are copies of Amaterasu's abilities, as a mockery of her. Ninetails can perform a charging headbutt across the arena, submerging its tails into the ground, following Amaterasu, in an attempt to spear her from below, raising its tails and spraying a toxic liquid, charging Ninestrike with dark energy before delivering a devastating slash, rapid slashes and stabbing with its own Dark Instrument, and last but not least, using the Celestial Brush with its techniques of Galestorm, Cherry Bomb and Icestorm.
Nothing of Ninetails' history prior to the events of Ōkami is known, other than the facts that it was the ruler of Oni Island, and that Yami had promised it to be lord of Ryoshima Coast. However, when Ninetails threatened the Dragonian race, King Wada used the Dragon Orb to harness the powers of the Water Dragon and rose to face it. Ninetails gravely wounded the Water Dragon, but in the process the Dragon was able to pull Ninetails' Dark Instrument, the Fox Rods, the source of its power, from its grasp and swallowed it before returning to the bottom of the sea. Weakened, Ninetails was forced to kill and impersonate priestess Rao of Ankoku Temple to enter Sei'an City and get close to Queen Himiko in order to kill her before she could find the location of Oni Island. With the help of Blight, it poisoned Sei'an City with a toxic fog. However, when Amaterasu and Issun turned up and threatened to overturn their plan, the evil demons were forced to get rid of the interlopers.
In the form of Rao, Ninetails had Amaterasu retrieve Rao's Prayer Slips, incredibly powerful paper slips capable of defeating demons which it needed to further its disguise. It then claimed that the Fox Rods were actually a powerful holy object sought after by Queen Himiko and claimed they were in the Sunken Ship, a wrecked ship in the ocean near Ryoshima Coast sunk by the Water Dragon. It helped Amaterasu enter the ship and, using Rao's Prayer Slips, helped her conquer the demons within, but this was actually a plot to lure in the Water Dragon to consume Amaterasu: indeed, when the Water Dragon began chasing them on the way back to shore, it used its supernatural abilities to escape and left Amaterasu to the dragon. However, unbeknownst to Ninetails, Amaterasu evaded the beast and used a holy device found in the Sunken Ship, the Lucky Mallet, to defeat Blight, whose defeat allowed Amaterasu to clear the mist from Sei'an City. Although Ninetails' plans were foiled, it now saw a chance to use Amaterasu in retrieving the stolen Fox Rods.
After an audience with Queen Himiko, Amaterasu ventured to North Ryoshima Coast. After much adventuring, she entered the Water Dragon and retrieved the Dragon Orb, a device which was said to be able to control the dragon. However, on the way, she also retrieved the Fox Rods. After the removal of the Dragon Orb, the Water Dragon died and Ryoshima Coast had now lost its guardian deity. 'Rao' then appeared and took the Fox Rods, claiming they would be used for good, and quickly departed.
Amaterasu gave the Orb to the Dragonian queen, Otohime. It was revealed that the Water Dragon had actually been Otohime's husband, King Wada, who had used the power of the Dragon Orb to confer upon himself the power of the Water Dragon. In light of these sad revelations, the King's spirit sent one last message to the heroes through the Orb. He showed them an image of Rao being attacked at Ankoku Temple. Not knowing if the vision was in the past or the present, Amaterasu raced to Ankoku Temple.
In front of Ankoku Temple, Amaterasu saw Rao, but she looked different, and moved like a ghost. Rao led Amaterasu to a secret cave with a well in it. Leaping down the well, Amaterasu found a secret tunnel containing the remains of a woman, wearing a very familiar nun's clothing. Continuing through the tunnel, the heroes ended up in a room of Queen Himiko's palace. However, they found that the handmaiden who was guarding the elevator to Himiko's quarters had been knocked unconscious. Hurrying to the queen, Amaterasu only found her lifeless corpse, with Rao standing near. Rao claimed the Dark Lord Ninetails had appeared and killed Himiko, but Amaterasu saw right through her lie. Pouncing at 'Rao', Amaterasu attacked the fake priestess only for her to dodge the wolf's attack. It was then that Rao's true form was revealed: Ninetails, the Dark Lord of Ryoshima Coast. The vision sent by King Wada had not been a call to protect Rao, but had instead shown the real Rao's death at the hands of Ninetails.
Ninetails attacked in a hybrid form, mixing Rao's body with its own fox mask and abilities. It also consumed Himiko's Crystal ball, in order to ensure that the last means to find Oni Island were lost forever. Amaterasu was able to defeat this creature, making it retch up Himiko's crystal ball, but Ninetails began to transform to its true form. However, the size of the room deterred its attack, and instead, it fled back to Oni Island, with its true power restored by the Fox Rods. All hope seemed lost, but Queen Himiko's spirit appeared in her crystal ball. She had planned this all along, and had harnessed Ninetails' dark powers when the evil kitsune had consumed the ball, allowing her to pinpoint the place Oni Island was set to appear. But Amaterasu had to reach the island by sunset, or the island would shift its position, and all hope of stopping Ninetails would be lost. As Himiko spoke those words, the crystal ball shattered. Paying the price for using Ninetails' dark powers, Himiko ascended to the heavens while praying for Amaterasu's success as she left the mortal plane. Amaterasu and Issun ran to North Ryoshima Coast, but were doubtful, as Himiko had also previously said that Oni Island was protected by a mystic barrier which only the now-deceased Water Dragon could penetrate.
As they arrived at Watcher's Cape they found Otohime, the Dragonians' queen, waiting for them. She had sensed Himiko's dying grief even from the depths of the sea, and knew what had to be done. The Water Dragon had died, but the Dragon Orb was the source of its power and, with a sincere prayer, Otohime could become the new Water Dragon and breach Oni Island's barrier. Utilizing the power of the Dragon Orb, Otohime became the Water Dragon, broke the barrier, and served as a living bridge to Oni Island. Amaterasu entered the dark palace and made her way to the top, retrieving a new Celestial Brush Technique, Thunderstorm, along the way. However, when she reached an altar at the very peak of the island, there was nothing but a very sinister fox-shaped constellation in the sky.
Amaterasu used her Celestial Brush to complete the constellation and in doing so, summoned Ninetails and challenged it to a battle. The demon kitsune presented itself as a god, to the point of mocking the Celestial Brush gods by fighting Amaterasu in an imitation of the realm in which the gods are summoned, as well as Amaterasu herself by using corrupted forms of her Brush Techniques and having its spirits adopt the form of the slain Rao.
After a fierce fight, Amaterasu defeated eight of the nine spirits that Ninetails consisted of (which resided in its tails), destroying Ninetails' illusions of godhood. After its godly façade dispersed, all that remained of Ninetails was a tired as well as beaten, yet ferocious beast, hungering for more power. However, without the added power of its eight tails, Amaterasu was able to pierce the kitsune's defenses and ultimately slay it. However, the dark, sinister shadow, which was what was left of Ninetails, flew back to the northern lands, along with Blight.
When Amaterasu entered the Ark of Yamato, she battled a revived Ninetails and defeated it once again, killing the devious kitsune forever.
"True form of the evil that dwells on Oni Island and seeks to destroy the Ryoshima Coast.
9 souls inhabit 9 tails, each acting independently.
According to legend, Ninetails can only be defended against with the Celestial Brush.
Burning the tails will temporarily weaken it,
and a lightning strike to the sword causes the souls to split apart.
Strike the final blow when the true form of the fox emerges."
In order to begin the boss fight, Amaterasu must complete the constellation in the sky, which is actually Ninetails pretending to be a god. After a short cutscene, the demon summons a false version of the heavenly realm where Amaterasu meets the Celestial Brush gods and begins the battle, which has two phases.
In the first phase, Ninetails fights with its many tails and with copies of Amaterasu's attacks. It can do a powerful charge (a copy of Amaterasu's headbutt), slash at Amaterasu with its Ninestrike sword, raise its tails and spray a toxic liquid from their ends, or send its tails underground to attack Amaterasu. If she tries to use any Celestial Brush techniques, Ninetails will use its own brush powers to try and cover up what she has drawn or use its own techniques (Cherry Bomb, Galestorm and Icestorm) to attack her; however, Amaterasu can prevent this by drawing quickly or closing the Brush screen before Ninetails can finish its own drawing.
Ninetails will periodically raise Ninestrike in an attempt to charge dark energy for a massive blow. By using Thunderstorm, Amaterasu must draw lightning to Ninestrike, splitting Ninetails into nine separate spirits. Each spirit takes on the appearance of a diminutive Evil Rao, but with distinct attributes and one of Ninetails' masks on its face. Amaterasu must attack the spirits and destroy them before Ninetails can reform its body. Most of the spirits will use Evil Rao's normal attacks, but the very fat one will just try and punch Amaterasu and the old one will simply limp across the battlefield. When fighting the first four spirits, the other four spirits not present will hover above the battlefield firing balls of energy that follow Amaterasu, and deal damage on contact. One spirit (Ninetails' "original" body/tail, being Ninetails' own spirit) will float above the battlefield, invincible; eventually, it will summon the remaining spirits to itself and reform Ninetails' body, minus the tails that Amaterasu destroyed as in their spirit form. All of the tails will be invincible during the reforming process, so Amaterasu will have to wait for Ninetails to raise Ninestrike once again to finish off the remaining spirits.
When eight of Ninetails' spirits have been slain, the heavenly realm illusion will dissolve and Ninetails will be forced to show its true form; a battered, one-tailed fox with a missing eye. Having lost most of its old attacks in this state, it will mostly use its charge attack, which is much faster than before. After a few charges, Ninetails will stop to catch its breath, giving Amaterasu a chance to get a few blows. Ninetails will also still attempt to charge Ninestrike, which gives Amaterasu a chance to hit it with Thunderstorm. This will cause Ninetails to take major damage and be stunned, leaving it vulnerable to Amaterasu's attacks.
When Ninetails' health is depleted, it will finally die, with Oni Island dissolving into sakura (cherry blossoms) petals.
It is fought again on the Ark of Yamato, exactly the same as before, except this time it is not released from a constellation.
Ninetails's gender is not clearly established. Although Ninetails disguises itself as a woman, it is consistently referred to as a "Lord" (claiming Yami promised that it would be "Lord of Ryoshima Coast"). This term is typically used to refer to males. However, Issun also calls it a "she", and occasionally refers to Ninetails using feminine slurs such as "Wench" (English Version), or "Bitch" (German Version). It could simply be that Issun only understood it by it's female form, and because he was still fuming about the real Rao and Himiko's deaths. Ninetails is also said to have occupied the body of a man before possessing Rao. Ninetails's gender tends to vary by source and language translation. In the Japanese translation of the game, Ninetails's gender is never clearly stated, never being referred to as male or female. In Japan, it is not even referred to as a "Demon Lord" as in the English translation, but instead a "Kyūbi no Yōko" (Literally "Nine-Tailed Fox Demon"). The German version of the video game refers to Ninetails using feminine pronouns. The English version of the official artbook refers to Ninetails using masculine pronouns, and in its true form it possesses a deep voice more reminiscent of the male characters in the game. Due to Ninetails's gender never being definitively established, the fanbase chooses to refer to Ninetails how they want to.
- When Ninetails uses the Celestial Brush, the ink it uses appears in red ink. Dark Chibiterasu has this exact ability as well.
- Just before it is released from a constellation, the moon is seen to be red, with a nine-tailed pattern. This is Ninetails' way of parodying how Amaterasu's finlets appear on the sun (such as when Sunrise is used and on the Day of Darkness).
- The reason why "Rao's" other eye is never seen is that Ninetails' true form has lost that eye.
- In the Ōkami Official Complete Works, it is stated that Ninetails is a demon who fancies itself as a god, hence the markings and unexpected ability over brush techniques. The boss stage is also based on the godly realm in which Amaterasu encounters Celestial Brush gods in.
- According to Japanese mythology, a kitsune's tails shows how old, wise, and powerful they are, with nine being the maximum. Also, when they obtain their ninth tail, they reach an all-knowing state (omniscience), which makes them achieve divinity. There are people who make offerings to kitsune as they would to a deity. This explains why Ninetails has godlike characteristics and has the godly realm when it appears. However, as his battle with Amaterasu proved, it isn't as powerful as a real god.
- Ninetails' godly form and arena are actually an illusion; after all the tails are defeated, Ninetails' true form is revealed and the boss arena turns back into the altar at the top of Oni Island. This could be symbolic of Ninetails losing its supposed "godhood" after losing its tails.
- In contrast to Ninetails' Bestiary entry, burning its tails with Inferno or Fireburst does not provide Amaterasu with any advantage in battle, since she can only hurt Ninetails when the tails are destroyed and the true tail is invulnerable to burning. The other eight tails will turn black when burnt, but will still attack normally and eventually return to their unburnt state.
- Ninetails' actions when during possession of Rao's identity are nearly identical to the legend of Tamamo-no-Mae, a courtesan of Emperor Konoe. According to the legend, Tamamo-no-Mae was very beautiful, always had a fragrant scent, and was very neat and clean. Despite her youthful appearance, she was very knowledgeable in all things and was quite intelligent. One day, the Emperor fell ill, and, after much investigation, it was revealed that Tamamo-no-Mae had poisoned him. In turn, she was revealed to be an incarnation of a supremely powerful kitsune, the White-Masked, Golden-Furred, Nine-Tailed Demon Fox (「白面金毛九尾の狐」?; Hakumen Konmō Kyūbi no Kitsune), which had manipulated rulers to sow discard throughout history in India, China, and Japan. She was then hunted down and slain.
- This reflects how "Rao" was eternally young and beautiful, as well as very knowledgeable, and, to a lesser extent, how she tried to kill the Emperor with the aid of Blight.
- Nine-Tailed Foxes were originally evil but later turned to be divine beasts and the signs of good fortunes in China before the legends were spread among other Asian nations (India, China, Korea, Vietnam, Japan) and evil characteristics, most notably transforming into beautiful women and troubling nations were added. Also, foxes, including Ninetails, have been worshiped as servants of gods and luck bringers. These facts may correspond with that the Ninetails in Okami possessed somewhat "god-like" characteristics including constellation and celestial Brush techniques.
This demon is another very famous character in ancient legends, so its inclusion in Ōkami was decided early on. However, I remember having a lot of trouble with its design. One day, I was rather suddenly struck with the thought of "an arrogant, excessively flashy character that fancies itself as a god", and that revelation quickly led to the white and red body, the battle in the heavenly realms, the unexpected ability to use brush skills, and other such characteristics that made this demon unique."—Hideki Kamiya (Illustrated Encyclopedia of Ōkami Concept Works, p.176, Ōkami Official Complete Works)