Well... where to begin with this girl?
Karin usually appears as annoying and prone to violent outburst, her usual victim being Suigetsu. However she, like many girls in Konoha before her, has a huge infatuation with Sasuke Uchiha. Her infatuation, however, is an unhealthy obsession to the point of fanaticism. For example, when Team Snake was resting in a village to take care of the wounded Sasuke after his battle with Deidara, Karin planned to use a drug on Suigetsu and Jugo to put them to sleep so she could rape Sasuke, and planned to keep one of his battered, sweat-drenched shirts for herself. (lol)

Karin lived in a small village that was burned out during a war. She was the only survivor, completely unharmed. Orochimaru came upon her after that and asked how she had survived, and she answered that she could tell huge groups of people were coming. Orochimaru then brought her to Oto, where she served him as a jailer at one of Orochimaru's bases. However, Sasuke had at some point noticed her at the time of his defection and had decided to use her in Team Snake long before he rebelled against Orochimaru. Unlike the rest of the team, Karin was indeed loyal to Orochimaru, going as far as to refuse to release Orochimaru's prisoners even after his defeat. Suigetsu has mentioned (perhaps as an empty threat) that Karin did something to Sasuke in the past.
Age: 16
Birthdate: June 20
Blood type: AB
Gender: Female
Height: 162.6 cm (1.626 m, 5.335 ft, 64.016 in)
Weight: 45.8 kg (100.972 lb)
She isn't perfect, we know that. But she is just hilarious and brings a whole new type of character to the manga, besides the fact that she may not be one of the most important among them. Whether you love her or even hate her, join the group and have your say about this chick. :DD