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.
The village he loves so much could be in chaos. Without Naruto, the symbol of hope and strength, the villagers might lose their morale. There could be power struggles as well, since Naruto was a major stabilizer in the political and social structure of the village. Also, his enemies might think they've won and become overconfident, which could actually work in Naruto's favor when he finally reveals himself, but in the short - term it could be a dangerous situation.
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.
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.
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.
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.
His body might not be fully adapted to the new bloodline right away. Just like when he first started using the Nine - Tails' chakra, there could be side effects. His chakra control could be thrown off, or he could experience physical pain when trying to use the new bloodline - related abilities until he fully masters it.
For Ron and Hermione, they would likely be devastated at first, thinking they had lost their best friend. But then they might start to suspect something when they notice small details that don't add up. Ginny would be heartbroken and might become more determined to fight against Voldemort in revenge. The Order of the Phoenix would be in chaos, with some members losing hope while others might start to investigate the circumstances of his 'death' more closely.
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.
He could be feared by the remaining ninja. Since he has killed all his enemies, others might see him as a ruthless killer rather than a hero. This could lead to isolation as people would be scared to approach him.