Kanna

was the first detachment of Naraku. As a "concealed incarnation" of Naraku, Kanna had no scent and no demonic aura, making her undetectable to Inuyasha's senses and was also immune to demonic aura-related effects such as the Hakurei-zan barrier. Kanna was the only incarnation that Naraku trusted with important information about his actions, allowing her to give orders in his place. Even though she was a void, she still had her own emotion of sadness that she could not express. She was created from Naraku after he had gathered enough Jewel Shards to make him strong enough to make incarnations.

Kanna and Kagura Arc
Kanna was seen walking with her mirror and some Saimyōshō towards a village, where she stole the souls of the inhabitants and turned them against Inuyasha and his friends. She was also tasked to take the Shikon Jewel fragment from Kagome but was unable to do so when her mirror almost burst, unable to contain with Kagome's soul. When Kagome fired one of her arrows into the mirror, Kanna was forced to release the villagers' and Sango's souls or risk its destruction. She disappeared along with Naraku and Kagura.

After her initial appearance she used her mirror to spy on various things for Naraku.

Shichinintai Arc
After Inuyasha was able to destroy Naraku's barrier he retreated to the sacred mountain, Mount Hakurei, but not before he resurrected the Band of Seven and recruited the mummified priest Hakushin to add additional reinforcement. With Hakushin, Naraku created the sacred barrier to mask himself within the mountain, and expel his human heart out of him to become invincible. Since Hakushin's holy barrier prevented Naraku, Kagura and all other demons inside the mountain from leaving, Kanna, having no demonic aura, was used along with Kohaku to give Naraku's orders to the Band of Seven. She also told Bankotsu how to make his weapon stronger by embedding the Shikon fragments in its blade.

During the time that Inuyasha battles with Jakotsu in the middle of the mountain, Kanna informed Kagura that Miroku and Sango had entered the mountain and were trying to find Naraku. Later, after Naraku's new body was formed, Kagura takes the infant to safety, while Kanna remained with Naraku until he successfully expelled Onigumo's Heart.

Akago Arc
Kanna's next task was to use the tainted Shikon Shard to control Kagome at the mountainside temple, a scheme that was once used by Tsubaki. Kagome, however still maintained her heart and rejected the shard. Kanna escaped along with the baby and Kagura on Kagura's plume.

When the baby was cut in half, Kanna took one of the halves that regenerated and told Kagura to take the one that would regrow into Hakudōshi, saying that Akago splitting in half was meant to be. Later, at a castle-town, a royal woman has a still-birth. Kanna then steals the souls of the vassals surrounding the woman, leaving only the mother alive. Kanna, along with Kohaku give The Infant to the woman, telling her that her child is actually alive, then wiping her memories. Naraku instructs Kanna and Kohaku to stay in the village, and protect the infant at all costs.

After Princess Abi attacks the castle, Naraku realizes his heart (the infant) is no longer safe at the castle. He ordered Kohaku to slay every inhabitant and Kanna to suck out their souls to prevent Inuyasha group from finding any information about Naraku's heart, or that the baby survived. After leaving the castle, Kanna, while holding Naraku's heart, ran into Kikyō on an unnamed mountain area and is attacked by Kikyō's sacred arrow. The baby was later given to Mōryōmaru, who killed and absorbed Goryōmaru per Naraku's command. While the rest of her siblings chose to betray Naraku, she was the one of the only ones who remained loyal to him. She felt sorry for Kagura because she had no real freedom.

Discovering Her own Heart
After Hakudoshi and Kagura's deaths and Byakuya's creation, she was ordered by Naraku to pretend to help Mōryōmaru strengthen his armor, telling him about twin demons, whose blood would make the armor even stronger. Naraku knew Akago couldn't read her mind due to the thought she doesn't have heart (Which is later proven not true). After this, Kanna remained unseen, as Naraku had no use for her at the time.

Following the death of Kikyo, Kanna ventured to the flower field where her sister incarnation had died, Reciting a poem, Kanna held Kagura's fan, wondering if she truly got the freedom she wanted. At that time, Kanna realised she had nothing herself. She walked off in the rain, until she reached a glistening pond; there, she tossed Kagura's fan into the water, bidding her farewell. It was at that exact time Byakuya arrived with Naraku's order to unleash the demon form of her mirror to combat Inuyasha's group.

In the manga, Kanna never performed a memorial of some sort for Kagura, she was waiting in a tree for orders when a gust of wind blew. She thought it was Kagura, but is was Byakuya with the very same order as stated above.

Kanna's End
"Fools. Do they pity Kanna? But Kanna cannot feel a thing, be it pain, fear or sorrow. She cannot even understand the reason for your pity." — Naraku

It becomes clear that she was fated to die by Naraku when she finally started to express her emotions (he reveals that her only purpose for existence is to destroy Inuyasha's group). In chapter 478 of InuYasha (Kanna's Gravestone), Kanna becomes more dangerous than anyone expected. She battles the group using a glass demon that came from her mirror. The glass demon copies the power of Tessaiga, robbing it of nearly all of its powers, including the Kaze no Kizu, Crimson Tessaiga, the Dragon-Scale power, and the Kongosōha, leaving the real Tessaiga nothing more than an apparent shell. It also appears that if the glass demon is hurt, the injuries are inflicted on Kanna since a black mark appeared on her neck after Kagome's arrow struck the glass demon in the same place with no apparent effect on it, and the same thing occurred when Inuyasha struck the glass demon's left shoulder, which turns the demon into a fighting voodoo doll.

When the group finds Kanna, she fires a ray of light from the sky down at Inuyasha. He reflects it with Tessaiga back at the glass demon. Kanna continues to receive damage to herself and the Tessaiga cracks from all of the light blasts. Kagome deduces that Kanna was ordered by Naraku to sacrifice her life in order to break Tessaiga. Because she continued to take most of the mirror demon's damage, Kanna indirectly loses her left hand and right arm during the battle; she also lost eyesight in her right eye. In chapter 480, she was forced to die at Naraku's command, by shattering herself and the glass demon into hundreds of shards.(In the anime, he destroys her heart.) A shard manages to hit Kagome's right eye and through the shard, Kanna communicates to her the secret to defeating Naraku.

Other than that, Kanna has never shown signs of betrayal to Naraku and was his most loyal, trustworthy detachment (besides Byakuya). In the anime though, it start to appeared sometime during the time Kagura left.

Although Naraku had commented upon Kanna's death that she had no thoughts and feelings; it was assumed that she did not care about either living or dying. However, after Kanna had communicated with Kagome just prior to her death, Kagome stated Kanna did not want to die and had feelings of her own. Kagome continues her wish to defeat Naraku and finally allows Kanna to rest in peace.

Legacy
Naraku managed to retrieve a shard of Kanna's mirror demon, insturcting Byakuya to give to Sesshomaru. Once the shard was crushed and sprinkled over Tenseiga, it allowed the blade to copy/ steal Tessaiga's abilities just as the mirror demon itself had done. The shard's remains were later removed by breaking Tenseiga against Tessaiga.

Personality
Kanna originally had barely any sense of self, doing as Naraku ordered of her. She knew Naraku could kill her and Kagura at any time he wished; "It's in Naraku's hands, both life and death." As she harbored no ill will towards her creator, she was trusted above all her siblings, being allowed to order Kagura and Kohaku around. Despite Naraku believing that she wouldn't develop a will or emotions of her own, Kanna did and began to question her own existence.

She appeared to have an ear for poetry, reciting some of the poems in Inuyasha the Movie 2. In the Final Act, Kanna recites two poems in Episode 1 and, once more when finding Kagura's fan in the flower field she died in.

Powers and Abilities
Kanna carried a mirror that could steal the souls of those reflected in it. Once a soul was trapped by her mirror, Kanna could control that person's body to carry out her bidding. However, the mirror could be overwhelmed by an especially powerful soul such as Kagome's. It couldn't steal souls from those who wear powerful items such as the Celestial Robe. It could also allow her to display what the Saimyosho are seeing or anything being reflected by a reflective surface. The mirror could also create a glass demon to copy the abilities of whatever it reflects, though Kanna herself suffered damage when the glass demon was wounded. Also when Kanna had summoned the glass monster she could create a shadow of her mirror to shoot rays of light at her opponent. She could even disappear and reappear at will indicating she also had Naraku's ability to teleport. She could use the mirror to create a powerful barrier that reflected any attack back.

Because Kanna was a nihility demon, she possessed no scent or jaki (demonic aura), making it impossible to detect her without actually seeing her. Naraku took advantage of this by using her as a spy and sending her on secret errands. Another benefit of this property was that she was completely, or nearly completely, unaffected by spiritual powers. During the Shichinintai arc, she was able to wander freely inside of St. Hakushin's purifying barrier while Naraku, Kagura and Naraku's minions were confined to Mt. Hakurei's interior.

Naraku
Kanna is seen throughout the series as the most trusted of Naraku's incarnations. Kanna's mindless, soulless actions and personality make her a very valuable minion to Naraku. She does not complain or wander or think for herself like all of the other incarnations of the series. This is confirmed when she states to Kagura that "We are nothing more than Naraku's tools."

In the beginning, he entrusts Kanna with stealing Kagome's soul, in order to put an end to her troublesome spiritual powers. Later in the series he trusts her with duties he thinks are unfit for Kagura, such as accompanying Kohaku while running Naraku's errands during the Band-of-Seven arc, and caring for Akago, who is later discovered to be Naraku's heart. After Kagura's death at Naraku's hands, Kanna begins to think about the meaning of her life and the possibility of her freedom. In the end, Naraku tries to sacrifice her in order to kill Inuyasha and his friends, but Kanna purposely fails in her last action and tells Kagome the secret to destroying Naraku for good.

Kagura
Although never stated, it is possible that Kagura and Kanna are very close, as Kagura never had any ill thoughts about Kanna, (but we do know she had unkind thoughts of Goshinki, Musō, The Infant, and especially of Hakudōshi.) Kanna and Kagura's possible closeness is supported in the 2nd movie, in that even after Naraku's "death", they remain together as opposed to parting ways after they both have their freedom. It is also possible that Kagura's betrayal and death inspired Kanna to betray Naraku. Kagura's death may have also caused Kanna to question her existence. They are the first two incarnations of Naraku, and both of them live the longest as compared to all the other incarnations of the series, many of which are killed after their first encounters with Inuyasha and his friends.

Kagome
At first, Kagome and Kanna were simple enemies with one trying to destroy another. But as the series progressed and after Kagura died, Kagome became more worried about Kanna. As shown during Kanna's final battle, when Kanna unleashed a mirror shadow on Inuyasha, Kagome warned Kanna about shooting the opening and when she died, Kagome screamed Kanna's name in clear disbelief. And after she died, Kanna spoke her last words to Kagome, telling her about the light that can kill Naraku.

Anime vs. manga
Kanna is given more characteristics in the anime than manga, as the reason for her to betray Naraku was because of Kagura. It was revealed that she started to develop her own emotion over time and before she died, she gave a smile because she finally had her own freedom. Also, when Naraku ordered Kanna to walk toward Inuyasha's group to kill them, she instead stood still and refused, proving that she does indeed have her own heart.

Quotes

 * "Your soul is mine."
 * "Her soul...won't be contained."
 * "The longer I endure this world, the more beautiful the midnight moon."
 * "Flowers wither and lose their hue, much as I reflect in vain time lost to the long rain."
 * "Kagura, did you become the wind? Did you win your freedom?"
 * "Kagome...the light...the light will kill Naraku."
 * "As I pass through the lengthy struggle of life in this fleeting world, I cannot help but long for the midnight moon I once saw."
 * "Freedom...?"
 * "It's in Naraku's hands. Both life and death."
 * "We are all merely Naraku's tools..."

Trivia

 * Kanna is the longest surviving detachment of Naraku's, outlasting all other incarnations except Byakuya, who is created shortly before her death. When she is first detached, she is Naraku's only incarnation and is so again for a short time in between Kagura's death and Byakuya's creation.
 * Her Korean voice actor Oh Ju-Yeon also played young Kaede.

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