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.
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.
One possible plotline could be that Naruto fakes his death to protect the village from a powerful enemy who has a vendetta against him specifically. He might do this to draw the enemy out and expose their weaknesses.
The Death Eaters might think they've won at first. There could be chaos and fear among the good wizards. But it could also lead to a secret resistance growing stronger.
One consequence could be that his friends are devastated at first. They might go through a period of grief and self - blame for not being able to protect him.
A secret organization that has been operating in the shadows and views Naruto as a major threat to their plans. They might be planning something big like taking over the ninja world, and Naruto's presence and influence stand in their way. So, Naruto fakes his death to gather intelligence on this organization without alerting them.
One possibility is that Harry uses some advanced and little - known magic. He could have found a spell in an ancient book in the Room of Requirement. This spell might allow him to project an image of his death while he actually hides himself in a magically protected space. He may also have made arrangements with the Order of the Phoenix to spread the news of his death convincingly.
One possible plot development could be that Naruto fakes his death to outwit a powerful enemy. He might go into hiding, secretly gathering information and allies to strike back at the right moment.
Another possibility is that the main antagonist is a group. It could be a secret organization that Naruto discovers is plotting something big. Since they are so powerful and well - connected, Naruto fakes his death to infiltrate them and expose their plans from the inside.
Well, he might use some substitution jutsu. He could replace himself with a log or something similar at the crucial moment, making it seem like he's been killed.