Travel back in time with a Feudal Farie Tale, InuYasha!

Kanna

Kanna, in the form of a small, pale girl, is the first, and longest lasting, of all of Naraku's incarnations, and the most trusted. Kanna is recognized easily by her emotionless expression and white clothing. Kanna is formed from mu, giving her neither yōkai properties, emotions, or a presence. Kanna seems fully aware of existing only as a servant to Naraku, though due to her lack of emotions, does not seem to care. Because of this, Kanna is the only incarnation Naraku truly trusts, telling her important information about his actions and allowing her to give orders to his other incarnations and pawns. His trust in her is also shown when it is hinted at that she is allowed to keep her own heart, as he had to tell her to destroy herself rather than doing it himself with her heart. Despite her loyalty, in Chapter 415 of the manga, Kanna appeared to have abandoned Naraku. Though Akago confirms this was done of her own free will, Kanna still remains loyal to Naraku.
Kanna carries with her a demonic mirror, with which she can steal the souls of those reflected in it. Once a soul is trapped within her mirror, Kanna can control their host bodies to her bidding. The people whose soul were stolen are almost unrecognizable from normal people. Should a powerful soul, such as Kagome's or Kikyo's, be locked into the mirror and overflow it, the mirror will start to crack, forcing Kanna to release all souls currently trapped within. It is later shown that the mirror can create powerful rays of light to blast at Kanna's enemies. The mirror has other purposes as well, such as reflecting any attack it catches(however it seems that one of the few attacks that Kanna's mirror can't reflect is Kagome's Hama No Ya as shown in episode 42 of the anime) or observing to goings on of the world. The most powerful of the mirror's powers, however, is the ability to create a glass demon that can copy the abilities of whatever it happens to reflect. Kanna, however, receives all damage in the glass demon's stead.
Interestingly enough, Naraku seems to always create his plans while keeping in mind not to have Kanna harmed, despite however an important role she plays. Naraku only uses Kanna twice for battle, the first being just after her introduction to test Kagome's soul, and the second being for her to destroy InuYasha's Tetsusaiga. During the latter attempt, in Chapter 480 of the manga, Kanna is ordered by Naraku to commit suicide, shattering herself and the glass demon she was currently using into thousands of tiny shards. One of the shards hits Kagome's right eye, and using it Kanna directs her final thought into telling Kagome how to destroy Naraku, the only time shown Kanna has betrayed Naraku. While Naraku comments Kanna had no care for either living or dying, Kagome states Kanna did not wish to die, and perhaps developed feelings of her own over time.

Sesshomaru

Sesshomaru is the yōkai son of the powerful Inu no Taishou and InuYasha's half-brother. Sesshomaru believes that struggle is the only way to survive, and throughout most of the series, he shows his contempt for InuYasha. Although Sesshomaru inherited his father's Tenseiga, which can bring a hundred people back to life with a single swing, he originally coveted InuYasha's inheritance, a powerful sword. However, a spell was cast on the sword so that a full yōkai cannot touch it without burning his flesh. Despite knowing that he cannot touch the sword, Sesshomaru still desires to take it from InuYasha. Throughout the series, Sesshomaru's compassion gradually grows as his rivalry with InuYasha decreases.

Kohaku

Kohaku is Sango's younger brother. When Kohaku turned eleven, his father told him that he must now put his training as a yōkai taijiya (exterminator) to use and help the rest of his family (who are also yōkai taijiya) with their next mission; exterminating a Spider yōkai who is tormenting a castle. Kohaku is scared, but he does not want to disappoint his father. Sango cheers him up by telling him he will be safe with her. However, during the mission something goes horribly wrong. Kohaku becomes a puppet of the Spider yōkai, who has taken the form of the castle's lord, and kills his family. Sango sees the spider thread the yōkai is using to control Kohaku connected to the back of his neck and knows he is not himself. Sango tries to wake her brother up and a battle ensues. They fight until the false Lord orders them killed. Sango is wounded and Kohaku is released from the yōkai's spell. He rushes to aid Sango, only to be shot dead by the Lord's archers. It isn't until after this that the lord's son, Hitomi Kagewaki (whose body is later taken over by Naraku), realizes that his father has been possessed and kills him and order's that the yōkai taijiya be given a proper burial. It is later revealed that this was all setup by Naraku so that he could use the opportunity in which the yōkai taijiya village's best warriors were absent to attack the village and take the shikon jewel shard there, then tell Sango that Inuyasha was the one responsible so that she would attack him.

Sota

Sota is the younger brother of Kagome, and is a third grade student. He is jealous of her adventures in the Sengoku Jidai, but Kagome claims it is too dangerous for him to accompany her. He once tried to go through the well but had no success.

Inuyasha's Transformations

Human
Like all hanyō, InuYasha turns completely human once a month. During the new moon his hair turns black, and he loses his supernatural powers, speed and defensive abilities as well as his demonic characteristics, such as his dog ears, claws, fangs, amber eyes and so on. In this form InuYasha can only use Tetsusaiga in its rusty form. Only InuYasha's friends and a few others know his secret as InuYasha tries to stay hidden during the new moon. He returns to his regular form when the sun comes out — he regains all of his powers: claws, fangs, strength, speed, and defensive abilities.

Demon
InuYasha's demon blood takes over anytime his life is in danger and the Tetsusaiga is out of reach. InuYasha first transformed when Naraku's detachment, Goshinki, broke the Tetsusaiga with its fangs. When transformed (pictured right), the white's of InuYasha's eyes turn red, while the other part turns blue with no pupil. Stripes appear on the sides of his face, and his fangs and claws lengthen. Once transformed, he gains a massive boost in all of his physical abilities, such as strength and durability, and becomes impervious to pain. He cannot, however, distinguish between friend and foe. If left in this state, InuYasha will continue killing until he is killed. Myōga reveals the reason InuYasha's father had the Tetsusaiga forged was to prevent his son's yōkai blood from taking him over since his hanyō mind cannot functionally handle the power he inherited from his father without being overwhelmed.

Purified
While trapped in the Stone Ogre's belly, InuYasha used a shard of the Jewel of the Four Souls to strengthen Tetsusaiga's power, an effort which backfired when the impure powers of the shard flowed through Tetsusaiga, causing InuYasha to transform. Kagome, seeing InuYasha's predicament, ran to him and her embrace purified the shard, leaving InuYasha in a purified version of his yōkai form. In this form, he retained some of the aspects of his yōkai form, such as the purple stripes on his face and the black patch under his eyes, but his eyes remained clear and he retained his sanity instead of being subject to the berserker rage which ordinarily characterizes his yōkai form. His yōki was increased exponentially, allowing him to utilize the Tetsusaiga's Adamant Barrage (fused with the Wind Scar) with an intensity far superior to previous usage. After the shard was removed from the Tetsusaiga, InuYasha reverted to his normal hanyō self.