Minati could be deeply saddened. If he has been following Naruto's journey, seeing him die would be like losing a friend. He might shed some tears and feel a sense of emptiness. He may also feel angry towards the circumstances or the character responsible for Naruto's death.
Minati's reaction could be complex. At first, he might be in denial, thinking that it can't be real. Then, as the reality sinks in, he could become very solemn. He might start to analyze the events that led to Naruto's death, thinking about what could have been done differently. And he may even be inspired by Naruto's sacrifice, if there was one, and vow to be stronger in his own life.
One possible plot could be that in a dark and alternate universe. Naruto might be facing an overwhelmingly powerful enemy that he simply can't defeat. Maybe an ancient evil has been unleashed and Naruto sacrifices himself to save the village. This would be a very tragic take on the Naruto story as he is usually seen as a symbol of hope and victory.
Naruto would probably be very excited and want to immediately start making changes for the better. He has always been about hope and improvement.
Sakura might be a bit surprised at first. She would probably tease Naruto a little about it, but then she'd also be curious to see what's in those fanfics. She might even start reading some herself to see how the fans portray her relationship with Naruto.
There could be a scenario where Naruto sacrifices himself to save Boruto or the entire Hidden Leaf Village from a catastrophic event like a massive attack by an unknown and dangerous force. He might use all his chakra to protect the village, leaving him with no energy to survive.
Hinata would be heartbroken. She has always loved Naruto deeply. She would probably be in a state of shock at first and then mourn for a long time. She might also try to keep Naruto's legacy alive, perhaps by teaching his ideals to the next generation of ninja.
He might be surprised. Fanfics can be full of wild ideas that he never thought of, like strange pairings or new jutsu concepts.
He may try to talk to Sakura and understand her reasons. Naruto is a character who believes in the goodness of people. So, instead of getting angry immediately, he would likely want to resolve the issue. He could also become determined to prove himself to Sakura, that whatever she thinks he has done wrong, he is actually not that person.
Naruto would probably be extremely hurt. He has always considered Hinata a friend and perhaps more. Betrayal from her would be a huge blow to his trusting nature. He might initially be in denial, not wanting to believe that Hinata could do such a thing.
Naruto would be deeply hurt. He would probably feel a mix of anger and sadness. At first, he might try to reason with Tsunade, to find out why she betrayed him.
At first, Naruto would be shocked and confused. His world view would be shattered. But then, he would draw on his inner strength. He has overcome so many hardships before. He might feel a deep sadness, but also a sense of resolve. He would still believe in the power of love and friendship, and use that to face Kushina's betrayal. He could also use this experience to grow even stronger and more determined to prove himself and his beliefs.