Karin

is a former subordinate of Orochimaru, who is now traveling with Sasuke Uchiha. She assisted Orochimaru in his experimentations and was left in charge of one of his bases while he was away.

Background
Karin lived in a small village that was burnt to the ground during a war. She was the only survivor, completely unharmed. Orochimaru randomly found her after that and asked how she survived, to which she answered that she could tell that huge groups of people were coming. Orochimaru then brought her to Otogakure, where she served as a jailer at one of his bases. Unlike the rest of the team, Karin was genuinely loyal to Orochimaru, going as far as to refuse to release Orochimaru's prisoners, even after his defeat.

Personality
Karin has a fluctuating personality; she will at times appear tough and in control, to the point of being violent, and at other times will appear highly flirtatious. She annoys Suigetsu, who she attacks whenever he voices his opinion of her.

She, like many girls in Konoha before her, has a huge infatuation with Sasuke Uchiha. Her infatuation, however, is an obsession to the point of fanaticism. For example, when Hebi was resting in a village to take care of the wounded Sasuke after his battle with Deidara, Karin planned to drug Suigetsu and Jugo to "ravish" Sasuke's unconscious body. She later revealed that she had kept one of Sasuke's sweat-drenched shirts. Karin also implied that a team consisting of just her and Sasuke would be much better than partnering with Jugo and Suigetsu. Suigetsu indicated that Karin had some history with Sasuke, but this has yet to be elaborated upon in the manga. In the anime, however, it was revealed that her crush on Sasuke began when she aided him in tracking down several prisoners that attempted to escape from Orochimaru. She seems to rate men on their chakra level, and claims that Suigetsu's chakra digusts her. Karin was very displeased when the Fifth Mizukage flirted with Sasuke, and called her an old hag for it.

Despite her crush on Sasuke, Karin currently fears him due to his cold and cruel attitude, as well as a darker chakra, and she questions what happened to him.

Appearance
Karin has red eyes, a matching hair color, and an unusual hairstyle: her hair is short and unkempt on one side, while long and combed on the other. She wears brown glasses, a lavender uniform common for Orochimaru's subordinates, short black shorts, and long black boots (in the anime, she has long black pantys along with open toes shoes).

Hunt for Itachi arc
Sasuke recruited her as a member of Hebi. While Sasuke admitted that she might be troublesome sometimes, he also noted that her special abilities made her useful. Once the team was completed, Sasuke sent Hebi out in multiple directions to try and locate Itachi Uchiha. While on the search, Karin passed Sakura Haruno, although the two did not acknowledge each other. After Deidara's suicide explosion, the rest of the team regrouped and took Sasuke to an inn to recover. When Karin went out for supplies, she sensed the Eight Man Squad approaching, and warned the team. It was her plan to use Sasuke's old clothing as a means to distract the squad from catching them. When they finally got back on Itachi's trail, Karin stayed behind with Suigetsu, Jugo, and Kisame as Sasuke went ahead to battle Itachi.

Hunt for the Eight-Tails arc
Hebi, now renamed Taka, later began working with Akatsuki. They were sent to Kumogakure to capture the Eight-Tailed Giant Ox's jinchūriki. When they found him, Karin stood on the sidelines and watched the others fight Killer Bee. When Sasuke was mortally wounded fighting Killer Bee, Karin immediately rushed to pull the dying Sasuke out of the fight, as Suigetsu and Jugo kept Killer Bee busy. As she pulled the swords out of Sasuke's body she exposed her right arm, riddled with numerous bite marks. She then told Sasuke to bite her arm, and as he did, her chakra healed his wounds.

As Killer Bee got bored and attempted to leave, Karin used her chakra-sensing powers to locate him. Killer Bee then used his demonic chakra to charge at her, Jugo, and Suigetsu, but Jugo rocketed them away to safety. After Sasuke was yet again critically wounded by Killer Bee, Karin tried to revive Sasuke again. She was stopped by Jugo, who claimed she didn't have enough chakra to save Sasuke from such a great wound; so he asked her to help him heal Sasuke. When Killer Bee fully transformed into the Eight-Tails, Sasuke used Amaterasu to quell it. Some of the flames spread to Karin's cloak, and Sasuke used his Mangekyo Sharingan to put them out. Karin was carried to safety by Jugo.

While the team was recovering, Karin briefly put her hair in a ponytail. She noticed that something was wrong with Sasuke, but as he brushed it off, she detected an enemy outside their base, which Sasuke and Jugo went to investigate.

Five Kage Summit arc
After Taka recovers, they move out for Konoha. Along the way they are stopped by Madara Uchiha, who convinces Sasuke to go after Danzo at the five Kage meeting. Upon their arrival in the Land of Iron, they decide to wait until the meeting is over before they attack. Zetsu soon reveals their presence and the Kage mobilize against Taka. When the battle gets under way Karin notices that Sasuke's chakra is now darker than his cursed seal level two chakra.

When the current Raikage arrives, he instructs Shī to locate and eliminate Karin, Taka's sensory ninja. Karin hides her chakra to avoid detection, and once Shī is defeated by Sasuke begins looking for Danzo's location. By the time Sasuke is able to elude the Raikage, Karin has found Danzo. She informs Sasuke that Jugo and Suigetsu are still alive, but he says to leave them and has her lead him to Danzo. Danzo flees as soon as they arrive, and Sasuke is forced to fight the Fifth Mizukage and Ōnoki before he can follow, with Karin calling the Mizukage an "old hag" for flirting with Sasuke. During the brief confrontation Karin grows concerned with Sasuke's deteriorating chakra levels. When his chakra signature disappears, she breaks into tears, believing him to be dead, with the Tsuchikage turning his sights on her.

Madara soon appears with Sasuke in tow, who sends him to a different realm. He sends Karin with him, telling her to heal his wounds.

Abilities
All of Karin's special abilities seems to derive from her excellent control of chakra. However, her level of control can be even unique. She can detect others' chakra, transfer her own chakra to heal others, and conceal her own chakra from others. Although she has avoided most battles thus far, as a former guard to one of Orochimaru's prisons she is presumably a capable battler, as evidenced by her effortlessly taking down a prisoner attempting to escape.

Karin's special ability, the Mind's Eye of the Kagura, allows her to track specific individuals through chakra, seen when she is able to discern that Jugo is not among a crowd of prisoners through the standard concentration pose for molding chakra. It also allows her to pick up chakra from long distances, and notice changes in an individual's chakra. Kakashi Hatake surmised that Karin is a particularly skilled chakra-sensing ninja, as she is not only able to tell that his group is approaching, but can also sense how many of them are present, and that one is a dog. Karin's senses can also tell when a person is lying from the fluctuations in that person's chakra made from dishonest emotions.

Karin also has the ability to heal others by letting them bite her and suck in her chakra. However, it is dangerous for her to use this ability more than once a day. It should also be noted that she has multiple bite marks on her arms, chest and neck which she wears long sleeve shirts to cover up, suggesting that she has used this power repeatedly.

It is said that she has the ability to completely suppress/hide her chakra from detection. However, doing so will render her unable to use chakra, thus disabling her Mind's Eye of the Kagura technique.

Trivia

 * Karin's name is made up of the kanji for "fragrance" or "perfume" and "phosphorus."
 * Karin's infatuation for Sasuke leads her to have a number of similarities with Part I Sakura Haruno.
 * Each tend to beat up their other teammate when angry. Sakura would beat up Naruto Uzumaki and Karin would beat up Suigetsu Hōzuki.
 * Both of them are also capable of healing their teammates, as Sakura became a Medical-nin. However, while Karin's ability allows her to heal through others biting her, she is not classified as a Medical-nin herself.
 * Both of them are very adapted in controlling chakra.
 * Both of them like Sasuke in a fan-girl like manner, although while Sakura's infatuation has matured into a sincere affection, Karin's is more or less obsession.
 * Karin has a hairstyle that resembles that of Ami.
 * According to the Third Naruto Databook:
 * Karin's hobby is collecting perfumes.
 * Karin's favorite food is Okonomiyaki, while she dislikes Gyōza.
 * Karin wishes to fight Suigetsu.
 * Karin will be a playable character in Naruto Shippūden: Narutimate Accel 3 and Naruto Shippuden: Ryujinki. Karin is seen using a unique Exploding Tag jutsu in Narutimate Accel 3.