The fanfic could have Naruto facing a new and unexpected threat, maybe a group of rogue ninja with extremely powerful and unknown abilities. They target the village's core, aiming to destroy it completely. Naruto steps up and battles them alone. As the fight progresses, he realizes that the only way to stop them is to use a forbidden technique that drains his life force. He makes the ultimate sacrifice. His death would change the village forever. His students, like Boruto, would grow up with the memory of Naruto's heroism and strive to be like him, while the village would create monuments and tell stories of Naruto's selfless act for generations to come.
In such a fanfic, the plot could involve a powerful and overwhelming enemy attacking the village. Naruto, being the hero, would fight with all his might. He might sacrifice himself by using a powerful jutsu that could stop the enemy but cost him his life. His death would leave the village in mourning, and his friends like Sasuke, Sakura, etc., would be deeply affected. They might then vow to carry on his legacy and protect the village even more fiercely in his honor.
Sasuke would be deeply affected. He and Naruto had a complex relationship. His first reaction might be shock and then a deep sense of loss. He might feel guilty for not being there to help Naruto. Sakura would be heartbroken. She had always cared for Naruto, and his death would be a huge blow. She might become more determined to protect the village in his memory. And Boruto, Naruto's son, would be devastated. He would probably grow up with a strong sense of purpose to live up to his father's sacrifice and protect the village even better.
Another idea is that Naruto's death while protecting Sakura causes a rift between Sakura and Sasuke. Sasuke might blame Sakura for Naruto's death in some way, either directly or because he feels Naruto wouldn't have been in that situation if it wasn't for Sakura. This could lead to a complex and angsty storyline where Sakura has to deal with the guilt of Naruto's death as well as Sasuke's coldness towards her.
One possible plot could be that Naruto is somehow transported to the Bleach universe. He meets Haku there, and they form a bond. When Haku is in danger from some powerful Bleach - related threats like Hollows or powerful Soul Reapers who misjudge Haku, Naruto steps in to protect him. In the process, Naruto, with his ninja skills but lacking the full understanding of the Bleach world's powers, gets overwhelmed and dies while trying to shield Haku.
Sakura would likely be devastated. Naruto has been her friend and teammate for a long time. His death would leave a huge void in her life, and she'd probably go through a long period of mourning.
Sasuke would be deeply affected. He and Naruto had a complex relationship. He might feel regret for not being there to help Naruto and also feel a new sense of purpose in avenging his friend. Sakura would be heartbroken. She had always cared for Naruto, and his death would make her question the purpose of the ninja life. Haku herself would be in a state of shock and disbelief. She would feel a heavy burden of guilt, knowing that Naruto sacrificed his life for her. She might become more withdrawn initially but then use Naruto's memory as a motivation to become stronger.
One possible plot could be that an ancient evil is awakened and sets its sights on destroying Konoha. Naruto, as the Hokage or a respected ninja, rallies all his friends and allies at first. However, as the battle progresses, he realizes that the only way to truly stop this evil is by giving his own life. So he makes the ultimate sacrifice, using his chakra to seal the evil away forever, thus protecting Konoha at the cost of his life.
One possible plot could be that Naruto and Haku are in a situation where an extremely powerful enemy attacks. Naruto, being the selfless hero, jumps in front of Haku to take a fatal blow. Haku is then left with the guilt and determination to carry on Naruto's will. She might vow to bring peace to the ninja world, just as Naruto had always dreamed. This could lead to Haku joining the Hidden Leaf and trying to bridge the gap between different ninja clans in Naruto's memory.
Well, Sasuke would probably be consumed by guilt. He might go on a self - imposed exile or a journey to avenge Naruto. The other characters would start to reevaluate their relationships with Sasuke. Konoha might be in a state of mourning, and there could be a power vacuum. Some might blame Sasuke for Naruto's death, which would add more conflict to the story.
One possible plot development could be that Sakura is deeply affected by Naruto's sacrifice. She might vow to carry on his will and become even stronger. In the story, she could use Naruto's death as motivation to finally achieve peace in the ninja world. For example, she could take on Naruto's dream of uniting all the villages and work towards it with all her might.
One possible plot development could be that Naruto sacrifices himself to save Ino from a powerful enemy. This might lead to a great sense of guilt among the other characters, especially those in Naruto's circle. Ino herself might be forever changed, vowing to carry on Naruto's will in some way. She could become more determined to achieve peace in the ninja world, inspired by Naruto's selfless act.