You are Naruto's younger sister and you both have a Nine tailed beast inside of you, Naruto and you were separated when you were younger and only you know you are siblings you are both a part of team seven with Sasuke and Sakura and Kakashi is the team's leader so he teaches team seven everything you need to know so you can be a ninja and today during training you decide to tell him

Naruto:wait we are siblings!?

Sasuke:I wasnt expecting that

Sakura:that explains why you look so simmilar