If Naruto dies in front of his sister in the fanfiction, it would be a very emotional and tragic moment. His sister might initially be in shock and disbelief. She could then experience a range of emotions like anger towards the cause of his death, whether it's an enemy or some unforeseen circumstances. As time passes, she might struggle with feelings of guilt, thinking she could have done something to prevent it. This event could completely change her character arc. For example, she might become more withdrawn or on the contrary, more determined to make a difference in the world. The fanfiction could then explore how she copes with this great loss and how it shapes her future actions and relationships.
In this kind of fanfiction, his sister would probably be devastated. She might go through a long period of grief and could potentially vow to avenge Naruto's death if it was caused by someone.
The story could progress with his sister seeking revenge if Naruto was killed maliciously.
Sasuke would be deeply affected. He and Naruto had a complex relationship, from being rivals to friends. He would likely feel a sense of guilt, as if he should have been there to protect Naruto. Sakura would be heartbroken. She had always cared for Naruto, and seeing him die in such a tragic way in front of his parents would make her feel helpless. His parents, on the other hand, would be in utter despair. His father might feel like he failed as a father again, not being able to protect his son this time either.
In the Naruto series, Naruto doesn't have a biological sister in the original story. So in this fanfiction, the author probably creates a new character to be his sister. It could be an original character with unique abilities and a complex backstory that leads to the situation where Naruto dies by her hand.
The Hidden Leaf Village would be in deep mourning. His friends like Sasuke would be filled with a mix of anger and grief. They might vow to protect Naruto's sister in his memory. The village would also probably hold a grand memorial for Naruto, and his story would become a legend to inspire future generations of ninjas.
Well, if Naruto dies in a Justice League fanfiction, it might start with Naruto being transported to the DC universe for some unknown reason. There, he might get involved in a fight that's too big for him to handle, resulting in his death. This could shock the Justice League members as they are not used to this type of ninja - like power. Batman would probably start investigating Naruto's origin and his death. Aquaman might be concerned about any potential effects on the oceans if Naruto's powers had something to do with water. Flash could be interested in how Naruto moved so fast. His death would be a major event that would disrupt the normal flow of the DC world.
In this kind of fanfiction, Naruto might find himself in a whole new world as a shinigami. He could use his ninja skills in unique ways. Maybe he'd have new powers related to the shinigami realm, like controlling souls in a different way than he did as a ninja. He'd also likely encounter different challenges and enemies that are specific to the shinigami world.
Perhaps Naruto is poisoned by a powerful new villain. His parents are revived just in time to see him succumb to the poison. This event could trigger a series of events where his friends and the entire village vow to avenge his death. His parents might then decide to stay in the living world to help in this quest for vengeance, despite the rules of the afterlife.
Hinata would be in shock. She'd probably freeze for a moment, unable to believe what she's seeing. Her eyes would be wide open in horror.
In such a fanfiction, Naruto could die in various ways. Maybe his sister is somehow possessed and attacks him fatally. Or there could be a situation where she accidentally causes his death during a fight due to a lack of control over her power.
In this fanfiction, Harry's encounter with his parents could be a very cathartic experience. He has been through so much pain and loss in his life. When he meets his parents, they would comfort him. They might talk about his friends and how they are going to be okay. His father could show him some cool magic tricks that he didn't get to learn while alive. And his mother would hold him tight, making him feel the love he has been longing for all his life.