Perhaps he could have some sort of dark - based chakra manipulation. Demons usually have unique chakra, and Naruto's demon part might allow him to use a different form of chakra that gives him new jutsu, like the ability to create shadowy clones or dark - energy attacks.
Well, Naruto could have a range of reactions. On one hand, he might feel a sense of isolation, thinking that he's different from all the other ninjas he knows. But on the other hand, his adventurous spirit could also make him curious about what this new part of him means. He might start to wonder about his powers and how they relate to his demon heritage. He could also be a bit scared, especially if he has been taught to fear demons in the ninja world.
In many fanfictions where Naruto discovers he has a sister, it often changes the entire dynamic of his story. It could give him a new sense of family and belonging that he lacked growing up. Maybe this sister was hidden away for some reason, like to protect her from Naruto's jinchuriki status bringing danger to her. This new relationship can also influence how Naruto approaches his ninja goals and his relationships with his friends.
The sister could also bring some new conflicts. For instance, if she has a different view on how the ninja world should be run compared to Naruto. This could lead to arguments and growth for both of them. Additionally, she might have her own set of friends or allies that Naruto has to get to know and work with, which would expand the cast of characters in the fanfiction and create more complex storylines.
In this kind of fanfiction, Naruto might initially be shocked. He would probably have to re - evaluate his whole identity. He has always seen himself as a ninja, but finding out he's a tailed beast would make him question his place in the ninja world. He might struggle with the idea that he is not just a human with a special power, but is in fact a tailed beast. This could lead to some interesting character development as he tries to come to terms with this new reality.
In some fanfictions, Naruto is completely devastated. He might go into a state of shock at first, unable to believe the news. Then he could be filled with intense grief and anger, blaming himself for not being there to protect Jiraiya.
In many fanfictions, Naruto is initially in a state of shock. He can't believe that Jiraiya, his mentor, is gone. He might go into a period of deep sadness and isolation, withdrawing from others as he tries to process the loss.
In some fanfictions, Naruto could find out in a very emotional way. For example, his daughter might be in danger, and when he discovers she is his, his feelings of love and the need to protect her are intensified. He might also struggle with the fact that he has missed out on part of her life so far. He'd then start to make up for lost time by spending as much time with her as possible, teaching her ninjutsu and sharing his own life experiences.
One possible plot twist could be Naruto's struggle to adapt to a different gender identity within the ninja world. He might face discrimination or confusion from his peers at first. For example, his male friends like Sasuke or Shikamaru might be initially shocked and not know how to act around him. However, Naruto's strong will would likely drive him to prove that gender doesn't define his abilities as a ninja. He could still pursue his dreams of becoming Hokage, but now also deal with the added challenges of being a female in a male - dominated society in the ninja world.