Karin

is a former subordinate of Orochimaru and presumably a former kunoichi of Kusagakure. 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 was disappointed to find she had the earth scroll as well, but she was able to catch a good glimpse of him before he left. She remembered the smile that Sasuke gave her.

According to 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 appear tough and in control at times, to the point of being violent and critical, and at other times will appear highly flirtatious. She annoys Suigetsu Hōzuki, whom she attacks whenever he voices his general opinion of her. She seems to be attracted to men based on their chakra level, and claims that Suigetsu's chakra disgusts her, Sasuke Uchiha's used to dazzle her, but it now scares her, and Naruto Uzumaki's seems to calm and dazzle her as well, though she also became scared when sensing the Nine-Tailed Demon Fox's chakra.

She, like many girls in Konoha before her, had been infatuated with Sasuke since they first met; when he saved her during the Chūnin Exams. In the anime, she has a flashback of when Orochimaru sends her to assist Sasuke in capturing a horde of escaped prisoners. There, she is captivated by the level of Sasuke's chakra and develops an infatuation with him. Karin's infatuation bordered on obsession to the point of fanaticism. For example, when Hebi was recuperating after Sasuke's battle with Deidara, Karin was planning to drug both 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 didn't 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 herself, she still found him attractive. However, after he stabbed her in order to kill Danzō and tried to kill her, Karin stated that she no longer cares about Sasuke.

She seems to be comfortable and relaxed around Naruto, noticing that his chakra is warm and bright. But, she starts to feel a dark chakra deep inside of Naruto, spooking her slightly.

Appearance
Karin has red eyes, a matching hair color, and an unusual hairstyle: her hair is short, pointy, and unkempt on the right side, while it is long, pin-straight and combed on her left side. 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, neck 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 has been praised by Madara Uchiha as being "helpful" for her abilities. Her 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. Sasuke noted her ability to sense chakra is unlike anyone else's. 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 also 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. This technique also causes those she heals to leave a permanent bite on her skin. 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, showing that she has used this power repeatedly in the past.

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. While Sasuke tried to recruit her, she tried to suduce him. 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 recovered, they moved out for Konoha. Along the way they are stopped by Madara Uchiha, who convinced Sasuke to go after Danzō Shimura at the Kage Summit. When they arrived in the Land of Iron, they decided to wait until the meeting was over before they attack. Zetsu soon revealed their presence and the Kage mobilize against Taka. When the battle got under way, Karin noticed that Sasuke's chakra was now darker than when in his cursed seal level two state.

When the Fourth Raikage arrived, he instructs C to locate and eliminate Karin, Taka's sensory ninja. Karin hid her chakra to avoid detection, and once C was defeated by Sasuke she again began to look for Danzō's location. By the time Sasuke is able to elude the Raikage, Karin had found Danzō. She informs Sasuke that Jūgo and Suigetsu are still alive, but he said to leave them and had her lead him to Danzō. Danzō fled as soon as they arrived, and Sasuke was forced to fight the Fifth Mizukage and the Third Tsuchikage before he could follow. During the brief confrontation Karin grew concerned with Sasuke's deteriorating chakra levels. When his chakra signature disappeared, she broke into tears, believing him to be dead, with the Tsuchikage turning his sight on her.

Madara soon appeared with Sasuke in tow before he sent them both to a different realm so she could heal his wounds. He later returned and released them in front of Danzō so that Sasuke could fight him. Karin observed the battle and tried to determine how Danzō was able to survive a series of apparently fatal injuries. She immediately ruled out genjutsu or a clone technique, and eventually noticed that the Sharingan embedded in Danzō's arm closed one by one as the battle progressed. Coupling this observation with frequent descents in Danzō's chakra levels, she learned the secret of his technique. She told Sasuke about it and advised that he keep his distance until Izanagi expired.

Once Sasuke mortally wounded Danzō, Karin healed his injuries. Danzō then took Karin hostage as he refused to die. Karin called to Sasuke for help, but Sasuke stabbed her through the chest in order to pierce Danzō's heart. Sasuke simply commented that, if she can be taken hostage so easily, she was now only a burden to him. Karin collapsed and Madara suggested that Sasuke finish her off since she had some knowledge of their plans. She took one last look at Sasuke, wishing to see his smile one more time, before he was about to kill her, but he was interrupted by the arrival of Sakura.

Sakura insisted that she wanted to be with Sasuke no matter what, leading Karin to realize that Sakura too loved Sasuke. Sasuke ordered Sakura to prove her loyalty by killing Karin. This, however, was a lie to make Sakura drop her guard. As Sasuke prepared to kill Sakura, Karin managed to mutter a warning, before Kakashi Hatake arrived to counter the attack. After it became clear that not even his words can alter Sasuke's motives, he ordered Sakura to take Karin away from the area and heal her enough to talk. While still barely conscious, Karin looked up at a sobbing Sakura and pleaded for her to hold in her tears. A tear fell down Karin's face as she sensed a further change in Sasuke's chakra, stating that Sasuke is no longer the person that Sakura once knew. As she asked Sakura what she will do, Sakura didn't respond and, emotionally unstable, returned to the fight despite Karin's warnings.

Later, when Sasuke prepared to fight with Naruto, Karin, sensing that Sasuke is going to over-exert himself again, dwelled on the fact that she was only able to heal him a little from his earlier skirmishes, before catching herself in that thought; in light of the fact of everything that Sasuke had done to her, Karin decided to herself that she was now done with Sasuke. After Sasuke left, Kakashi told her that she was coming with them to Konoha; Karin resigned to her fate as she had no choice, being warned by Kakashi not to try anything. As Karin left with them, she made a special note of Naruto's character, apparently hearing of him before.

Fourth Shinobi World War arc
When they met up with Kiba Inuzuka, Rock Lee, and Sai, Karin defended Naruto from Sakura by reminding her that she was (indirectly) the one who poisoned Naruto, due to him fainting from it. She also noted that Naruto's chakra was the exact opposite of Sasuke's - warm and bright. But when she looked closer, she saw that there was an evil chakra inside of him. Later, she is interrogated by Ibiki Morino in Konohagakure to get information on Sasuke and Kabuto Yakushi.

Trivia

 * Karin's name is made up of the kanji for "fragrance" or "perfume" (香) and "phosphorus" (燐).
 * Karin's infatuation for Sasuke lead 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 have a short temper.
 * 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 liked Sasuke in a fan-girl like manner, although while Sakura's infatuation has matured into a sincere affection, Karin's was more of an obsession.
 * 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 jutsu in Ultimate Ninja Heroes 3 are 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 herself about Sasuke) " ...I just wanted... to see that face once more..."
 * (To herself about Sakura) "You're the enemy...I don't want to sympathize with you...so...so don't...don't cry like that in front of me...! Damn it..."
 * (To herself about Sasuke) "Sasuke... I may have healed you a little, but this is too much... actually... forget it, I'm done with you."