The Land of Whirlpools had once been a renowned country in the shinobi world, maintaining generations of friendship with Konoha in the Land of Fire. Within its borders, Uzushiogakure had been famous throughout the world for the Uzumaki Clan's Sealing Jutsu.
But those good times had not lasted. The power and unusual nature of their Sealing Jutsu had made many forces in the shinobi world wary of them.
After the First and Second Hokage passed away, successive Shinobi Wars had left Konoha too overwhelmed to look after anyone else.
At the time, Uzushiogakure had also been suffering from a shortage of talent to succeed the older generation. Numerous countries and clans invaded, and in an extremely short time, the Land of Whirlpools met with utter destruction.
Only a tiny handful of the Uzumaki Clan escaped with their lives. The vast majority of its members lost their lives in the massacre in the Land of Whirlpools.
There were only a few survivors, and Karin's mother had been one of the lucky ones who managed to escape.
Her mother, still young back then, had hidden in the ruined Land of Whirlpools for a long time. Eventually, when she could no longer survive there, she endured countless hardships and finally escaped the country.
But that had not saved her. After she drifted into Kusagakure, the Grass Ninja discovered her mother's special Uzumaki constitution: simply biting her body allowed them to receive chakra and heal their wounds. This once again put the mother and daughter in a precarious position.
To secure a place where they could survive, and to give her daughter a peaceful life, her mother sacrificed herself, volunteering to become a human medicine pill for the Grass Ninja.
In the end, the Grass Ninja used her mother like medicine until she exhausted