Karin

Karin (香燐) is a former subordinate of Orochimaru who assisted him in his experimentations and was left in charge of his south base while he was away; and was also the only one loyal to Orochimaru to remain even though her current status is questionable. She has red eyes, matching hair color and an unusual hairstyle; her hair is short and unkempt on one side, and long and combed on the other. Karin will at times appear tough and in control, and other times will appear flirtatious. Karin's name means 'intense sulfur' and is also a homonym for the fruit 'quince'.

Sasuke Uchiha recruits her as a member of Snake. While Sasuke admits she may be troublesome, he also notes that her special abilities make her useful. She also seems to have a liking for Sasuke, implying to Sasuke that a team consisting of the two of them would be much better than one with Suigetsu or Jugo. She has an unhealthy interest in Sasuke, as she goes so far as to keep one of his battered, sweat-drenched shirts for herself and plans to "ravage" him after everyone falls asleep. Suigetsu notes that something once happened between her and Sasuke though what this means remains unclear, since Karin punches Suigetsu before he can finish his sentence. As for other relationships, Karin is cautious around Jugo due to his condition and constantly finds fault with Suigetsu's actions and motivations. In turn, Suigetsu often makes rude comments about her actions and motivations, resulting in her beating him until stopped by another teammate.

Karin's special ability 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 surmises 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.

(Taken from Wikipedia.)