Karin Profile Review
Karin is a former subordinate of Orochimaru who assisted him in his experimentations. After learning of his death she remains loyal to him by keeping the prisoners of the base she is stationed at in check. Karin 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. She will at times appear tough and in control, particularly when Suigetsu or Jugo are present. When Sasuke Uchiha is around, however, she switches to a flirtatious personality where she tends to imply a team consisting of only the two of them would be considerably better. She has a dramatic and sometimes almost obsessive 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. (Source From Wikipedia)
Karin Abilities
Karin's special ability allows her to track specific individuals through chakra, as seen when she is able to discern that Jugo is not among a crowd of escaped prisoners. 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. (Source From Wikipedia)