Karin was one of the subordinate Orochimaru or rather ex-subordinates Orochimaru, and also a former kunoichi from konohagakure, she helped Orochimaru in the experiment. After Orochimaru died, she was traveling with Sasuke Uchiha and he helped sasuke revenge on Itachi!
Karin also took part in the Chunin Exams held in Konoha as one of the participants. During the second stage, which took place in the Forest of Death, he lost track of his colleagues and was attacked by a large bear. He was saved by Sasuke Uchiha, who was disappointed to find that he has a scroll seal, which he was able to catch a glimpse of good before he left. He remembered the smile that gave Sasuke!karin very beautiful, and I think the manga is not so beautiful ~ ~ greeaaaaaaatt cosplay!!