One possible reason could be to protect his family. After the war, Naruto might have made many enemies. By faking his death, he could draw the attention of these enemies away from his family, especially his wife and children. His enemies would think he's no longer a threat and stop targeting his loved ones.
Well, Naruto could have made a deal with some powerful being or used some sort of forbidden technique. Maybe he found a way to transfer his life signs to another object or being, making it seem like he was dead. He's always been resourceful and full of surprises, so faking his own death in a really elaborate and unexpected way is not out of the question.
His friends might feel betrayed. They would be mourning his death while he was actually alive. This could lead to a lot of anger and mistrust when they find out the truth.
Your question is not clear enough. Why did Yuan Zhibang fake his death in the novel Death Notice? I need more context information to answer your question.
If you can provide me with more information about the novel Death Notice, I will try my best to answer your questions.
Sakura would be extremely angry at first. She has known Naruto for a long time and would feel betrayed that he didn't trust her enough to tell the truth. But later, she would understand his reasons and might even help him if she could.
Perhaps it has to do with a new and mysterious disease. In fanfiction, new and unique diseases can be created. This disease could be something that attacks his unique chakra system, which is different from others. Since his body is so reliant on chakra, if the disease disrupts it enough, it could lead to his death.
You could have the character stage a scene that makes it look like a fatal accident. Maybe they fake their own disappearance and leave behind clues that suggest death.
Well, in some fanfictions, he might get it from a skilled ninja prosthetics maker. This maker could be someone who specializes in creating artificial limbs for ninjas who have lost their arms in battle.