Well, in such a fanfiction, Kakashi might be really angry when he discovers Naruto has been abused. He could use his skills to protect Naruto and find out who the abuser is.
Well, Kakashi is a complex character. When he discovers Naruto is abused in the fanfiction, he may first feel a deep sense of guilt for not noticing earlier. He'd then use his skills and influence in the village. He could start by reporting it to the proper authorities in Konoha, like the Hokage. And at the same time, he'd be there for Naruto, providing emotional support, talking to him, and helping him through the trauma. Kakashi has his own past traumas, so he'd understand what Naruto is going through on some level.
There is no such official story in Naruto. The main focus in Naruto is on Naruto's growth, his friendships, and the overall plot related to the ninja world, not such an uncharacteristic and potentially inappropriate relationship.
Once Kakashi finds out Naruto is abused in the fanfiction, Naruto's life takes a turn for the better. Kakashi would become a more constant presence in his life. Naruto would no longer have to fear the abuse continuing. He'd be given a chance to focus on his growth as a ninja and as a person. Kakashi would introduce him to positive influences in the village, like wise elders or kind - hearted villagers. Naruto's self - image would improve as he realizes he is worthy of protection and care. His living situation might also change, perhaps moving to a more secure and comfortable place. And his dreams of becoming Hokage would seem more achievable as he overcomes the trauma of the abuse with Kakashi's help.
In this fanfiction, perhaps Naruto confronts Kushina about the secrets she kept from him. For example, if there were things she knew about his powers or his destiny that she didn't share before her death. He could be feeling betrayed and wants answers.
Naruto's reaction could be complex. Since he has his own feelings for Sakura, this situation could stir up a lot inside him. He might initially be a bit hesitant in how to approach her because he doesn't want to overstep any boundaries. But in the end, his natural instinct to help a friend would take over. He would listen attentively to Sakura, his eyes full of determination to make her feel better, and use his own unique way of thinking to give her advice or just be a shoulder to cry on.
Well, family or father - son relationship is a big theme. Kakashi becomes a father - like figure to Naruto, providing the love and support he never had. Another is the transformation of Naruto. From a traumatized and potentially broken child, he becomes a strong and confident ninja under Kakashi's care. Also, the exploration of Naruto's hidden potential is a common theme. Kakashi, being perceptive, unlocks Naruto's abilities that were perhaps stunted by the abuse.
It could be that there is no traditional antagonist. The conflict might be internal, with Naruto's own emotions towards Kushina being the main source of drama.
There might be. Fanfiction writers often like to play with the established relationships in the Naruto universe. Since Naruto has a complex world with many interesting characters, it's not unusual for someone to write a story where Naruto becomes Kakashi's sensei in an alternate timeline or some other creative scenario. It could be an interesting take on the characters' development and the overall story.