Karin's mother was an Uzumaki clan member who ended up in Kusagakure after her home village was destroyed. She arrived while Karin was still young, and the village allowed her to stay on one condition: she'd use her abilities to heal the injured.
Being a direct Uzumaki descendant gave her an unusually powerful life-force. This meant exceptional vitality, longevity, and potent healing abilities. What really set her apart was a unique trait—anyone who bit her and drew in her chakra would be instantly healed of their wounds. It's the kind of ability that made her indispensable to a village, and likely why Kusagakure was willing to take her and her daughter in.
Content compiled by AnimeList.moe from publicly available sources.
