Hinata might be shocked at first. She has always adored Naruto, and this sudden act of aggression from him would leave her stunned and unable to process it immediately.
Hinata would be overjoyed. She has loved Naruto for a long time, so his proposal would be like a dream come true for her. She might start crying tears of happiness and immediately say yes without hesitation.
Hinata might be very hurt. She's a sensitive person, so Naruto yelling at her could make her feel small and sad. She might start to doubt herself and her abilities.
Naruto, being the energetic and battle - loving guy he is, would likely be on the edge of his seat, eager to see who comes out on top in each death battle. He might be making bets with himself about the outcomes. Hinata, with her gentle nature, would be a bit more subdued. However, she would also be intrigued. She might be more concerned about the safety of the fighters, even though it's just a fanfiction battle. And when a fight gets really intense, she might clutch Naruto's arm without realizing it, while Naruto is too engrossed in the action to notice at first.
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.
At first, Naruto would be completely shocked. He has always seen Hinata as a loyal friend and someone who has deep feelings for him. So the idea of her betrayal would be hard to fathom. He might try to deny it at first.
He would be filled with rage. Naruto has a strong sense of justice and the fact that someone took Hinata away from him would fuel his anger. He would vow to find and punish whoever was responsible. He might even become reckless in his pursuit of vengeance, endangering himself and those around him. His friends would have to step in to try and bring him back to his senses.
Hinata would likely be conflicted. On one hand, she still has feelings for Naruto, but on the other hand, she can't tolerate his arrogance. So, she would start by observing him from a distance. As she notices how his arrogance is affecting others, she would gather the courage to approach him. She would tell him how his actions are not in line with the values he once held dear, like friendship and protecting the weak. And she would hope that her words would make him reflect on his behavior.
He would be filled with a deep sense of grief. Naruto has always cared about Hinata, and her death would be like a part of him has been ripped away. He might isolate himself for a while, blaming himself for not being able to protect her. But eventually, he would use his pain as motivation to get stronger and fight against whatever caused her death.