Everyone talks about how Minato trained Team Seven, and Jiraiya trained Minato... but what if Kushina had student, a girl she saved from a local attack and trained hard to help her never be helplesss.

The girl eventually becomes a ronin, and moves to Mist to help the Civilians. She helps Mei win the war...

Eventually, during the Wave arc, she goes to collect Zabuza and finds Naruto. She knew Kushina was dead but never knew she had a kid. She immediately comes to adopt Naruto, especially after finding out how badly he has been treated. She is a powerful kunoichi with tremendous experience and trains him and his friends to a high level.

Her name is Kanade.

She is a master swordswoman, a master sealer and is well trained in Water, Wind and Lighting chakra. She is called the Laughing Storm. She is of a Civilian bloodline but is powerful anyway.

Just a base idea...