One possibility is that Naruto gets caught in a powerful genjutsu that makes everyone forget him. He might then struggle to find a way to break the genjutsu on his own. He could start to question his own identity and purpose, as being an Anbu, his very existence in the shadows becomes even more lonely without anyone's recognition.
It could be Orochimaru. He has always been interested in powerful jutsus and Naruto's unique power as a Jinchuriki. He might have developed a new jutsu to make everyone forget Naruto so that he can capture him without interference for his own experiments.
Initially, Naruto would be in shock. He'd try to talk to his friends like Sasuke or Sakura, but when they look at him with blank stares, it would break his heart. He would feel like an outsider in his own village. But then, his ninja spirit would kick in. He would start investigating. He might think it has something to do with a new enemy or some hidden plot. He'd be on a mission to not only get his friends and family to remember him but also to protect the village from whatever threat caused this forgetting in the first place.
One possible reason could be a powerful genjutsu cast over the village. Maybe an enemy ninja with strong illusionary powers managed to make everyone forget Naruto. It could also be due to some sort of curse. For example, a dark curse was placed on Naruto that made people's memories of him fade away gradually.
Naruto's adaptation to the Anbu in this fanfiction could be a complex process. At first, he'd probably struggle with the strict discipline and the need for secrecy. But his previous experiences in tough situations would come in handy. He'd gradually understand the importance of stealth and how to use his skills in a more covert way. He might also learn from the more experienced Anbu members, and his own determination would drive him to become a valuable part of the Anbu.
Some of the more hot - headed ANBU members might overreact and assume Naruto is a threat to the village. They could try to use force to get the stolen item back. However, the more level - headed ones might try to figure out Naruto's motives first. They might consider that Naruto could have a good reason for what he did, like if he thought the item was being misused by the ANBU.
One interesting storyline could be Sakura joining the Anbu and having to prove herself among the male - dominated group. She might face challenges like secrecy requirements and intense training, all while Naruto is on his own journey, and their paths cross in unexpected ways during missions.
Well, Kakashi could train Naruto in combat skills specific to ANBU missions. This would include more lethal and precise attacks. He might also teach Naruto how to use different types of weapons that are common in ANBU operations. Maybe Kakashi would set up mock battles where Naruto has to face multiple opponents at once, just like in real ANBU scenarios.
There could be. Given the popularity of Naruto, many fans like to create alternative storylines. The idea of Naruto as a child in the Anbu is quite appealing as it would be a deviation from the original story. It might explore how he would interact with the more secretive and elite members of the Anbu, and how his presence would affect the Anbu's operations. It could also delve into his relationships with other characters in this new setting.
These fanfictions often have a darker and more serious tone compared to the regular Naruto story. Since the Anbu deal with dangerous and often covert missions, there are more high - stakes situations. For example, Naruto might have to make tough decisions that go against his usual moral code in order to complete a mission. Also, they usually explore Naruto's relationships with other Anbu members in depth, like how he forms new alliances or rivalries within the organization.