Karin

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

Background
Karin took part in the Chūnin Exams that were held in Konoha in Part I. During the second phase, taking place in the Forest of Death, she lost track of her teammates and was attacked by a large bear. She was saved by Sasuke Uchiha, who she was able to catch a good glimpse of before he left. She remembered the smile that Sasuke gave her.

According the the third Naruto databook, Karin lived in a small village that was burnt to the ground during a war. She was the only survivor, completely unharmed. Orochimaru found her after 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 and, in the anime only, have them killed for speaking of his death, 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 general opinion of her. She seems to rate men on their chakra level, and claims that Suigetsu's chakra disgusts her.

She, like many girls in Konoha before her, has been infatuated with Sasuke Uchiha since they first met; when he saved her during the Chūnin Exams. According to the anime, her interest in him began when they tracked down some of Orochimaru's escaped prisoners together. Karin's infatuation borders on obsession to the point of fanaticism. For example, when Hebi was recuperating after Sasuke's battle with Deidara, Karin planned to drug Suigetsu and Jūgo and then "ravish" Sasuke's unconscious body. She later revealed that she had kept one of Sasuke's sweat-drenched shirts. Karin does not make much of an attempt to hide her feelings, frequently suggesting to Sasuke that they should spend time alone. Karin was similarly very angry when the Fifth Mizukage flirted with Sasuke, and called her an "old hag" for it. Despite Sasuke's chakra becoming increasingly "darker" according to Karin and his trying to kill her, she still finds him attractive.

Appearance
Karin has red eyes, a matching hair color, and an unusual hairstyle: her hair is short and unkempt on her right side, while long and combed on her left. She wears brown glasses, a lavender uniform common for Orochimaru's subordinates, short black shorts, and long black thigh high stockings with shoes. Throughout her chest and arms are bite marks that result from using her Heal Bite, and all of which are covered by her uniform.

As she is allied with Hebi Karin begins to wear a pouch around her midsection, and later a black cloak. When allied with Akatsuki, Karin wears an Akatsuki cloak with a hood instead of a high collar. After Taka's fight with Killer Bee, Karin briefly put her hair in a ponytail.

Abilities
Karin's special ability, the Mind's Eye of the Kagura, allows her to track specific individuals through chakra simply by using her standard concentration pose for molding chakra. For example, she was once able to discern that Jūgo was not among a crowd of prisoners by chakra alone. 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. She can use her ability to determine if someone is lying by the fluctuations in that person's chakra made from dishonest emotions. She can also find out if an enemy is using a clone jutsu and indicate if someone, including herself, is trapped in genjutsu. She can, similarly, conceal her own chakra from others. However, doing so will render her unable to use chakra, thus disabling her Mind's Eye of the Kagura technique.

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 are covered up by the long sleeve shirts she wears, suggesting that she has used this power repeatedly.

Although she has avoided most battles thus far, she is presumably a capable fighter, as she was effortlessly able to prevent a prison break at one of Orochimaru's prisons. She was also strong enough to move all three of her teammates out of the way of an attack at once. She also was able to take a very hard kick from Danzō that launched her from a great height into solid rock without losing consciousness. Karin is praised by Madara Uchiha as being "helpful" for her abilities and that he made the right choice of bringing her along.

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, Jūgo, 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 Jūgo 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 Heal Bite healed his wounds.

As Killer Bee got bored and attempted to leave, Karin used her Mind's Eye of the Kagura to locate him. Killer Bee then used his demonic chakra to charge at her, Jūgo, and Suigetsu, but Jūgo rocketed them away to safety. After Sasuke was yet again critically wounded by Killer Bee, Karin insisted on reviving Sasuke again. She was stopped by Jūgo, who claimed she didn't have enough chakra to save Sasuke again, so Karin watches as Jugo transfers his flesh to Sasuke to heal him. When Killer Bee fully transformed into the Eight-Tails, Sasuke used Amaterasu to quell it. Karin quickly moved all of her teammates out of the way of one of Killer Bee's tentacles, but this resulted in her being hit by one, and some of the black flames spread to Karin's cloak. Sasuke used his Mangekyō Sharingan to put them out. Karin was carried to safety by Jūgo.

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 Jūgo 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 Danzō at the Kage Summit. 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 when in his cursed seal level two state.

When the Fourth Raikage arrives, he instructs C to locate and eliminate Karin, Taka's sensory ninja. Karin hides her chakra to avoid detection, and once C is defeated by Sasuke she again begins looking for Danzō's location. By the time Sasuke is able to elude the Raikage, Karin has found Danzō. She informs Sasuke that Jūgo and Suigetsu are still alive, but he says to leave them and has her lead him to Danzō. Danzō flees as soon as they arrive, and Sasuke is forced to fight the Fifth Mizukage and the Third Tsuchikage before he can follow. 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. He later returns and releases them in front of Danzō so that Sasuke can fight him. Karin observes the battle and tries to determine how Danzō is able to survive a series of apparently fatal injuries. She immediately rules out genjutsu or a clone technique, and eventually notices that the Sharingan embedded in Danzō's arm close one by one as the battle progresses. Coupling this observation with frequent drops in Danzō's chakra levels, she learns the secret of his technique (Izanagi). She tells Sasuke about it and advises that he keep his distance until Izanagi expires.

Once Sasuke mortally wounds Danzō, Karin heals his injuries. Refusing to die, Danzō takes Karin hostage. Karin calls to Sasuke for helps, but Sasuke stabs through her in order to pierce Danzō's heart. Sasuke explains that, if she can be taken hostage so easily, she is only a burden to him. She collapses and Madara suggests that Sasuke finish her off since she has some knowledge of their plans. She takes one last look at Sasuke, wishing to see his smile one more time, before he is about to kill her, but he is interrupted by the arrival of Sakura Haruno.

Trivia

 * Karin's name is made up of the kanji for "fragrance" or "perfume" (香) and "phosphorus" (燐).
 * 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. Though Karin's ability allows her to heal others through letting them bite her, she is not classified as a Medical-nin herself.
 * Both of them are very adept 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 of an obsession.
 * Both of them begin to fear Sasuke for the darkness within his heart, though Sakura has seemingly lost hope, Karin still cares for him.
 * 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 is a playable character in Naruto Shippūden: Ultimate Ninja Heroes 3. Her ultimate jutsu in Accel 3 is focused on her Mind's Eye of the Kagura technique.
 * Karin is a support character in Naruto Shippūden: Ryujinki, and appears in a new outfit, like most of the characters.

Quotes

 * (To Sasuke) "Sasuke... Is this all I am to you...?"
 * (To Sasuke) " ...I just wanted...To see that face once more..."