One possible plot could be Naruto facing the internal politics of ANBU. He might struggle to adapt to their more secretive and sometimes morally gray operations compared to his usual straightforward ninja way. For example, he could be assigned to a mission where he has to spy on a former ally, creating an internal conflict within him.
Maybe Naruto joins ANBU to keep an eye on potential threats to the village that emerged after the war. He could use his new position to try and build bridges between different ninja clans and villages that are still suspicious of each other. He might start by recruiting some of his friends from other villages for joint training exercises within the ANBU framework.
In such a fanfiction, the plot could involve Naruto being constantly overlooked by the village. Fed up with this, he decides to join ANBU to prove his worth. He might face challenges like distrust from his ANBU comrades at first because of his reputation. But as he goes on missions, he shows his skills and determination, gradually earning their respect and changing their perception of him.
Well, in such a fanfiction, perhaps Naruto has just lost Sasuke again and is deeply depressed. The ANBU, seeing his skills and his need for a distraction, recruit him. He starts off being a bit of a misfit in ANBU, not following all the rules because of his independent nature. But as he continues, he starts to understand the importance of their work. He might even form new bonds with his ANBU comrades, which slowly help him come out of his depression.
Well, in a fanfiction where Naruto joins ANBU, his training would intensify. He'd be trained by some of the toughest ANBU veterans. His skills in combat would become more refined as he'd learn to use weapons like kunai and shuriken with more precision. He may also develop new jutsu that are more suitable for covert operations. His growth as a ninja would be different from the regular path, focusing more on secrecy and assassination if required.
If Naruto joins ANBU after the war in fanfiction, it could lead to some interesting character developments. He would have to deal with the darker side of the ninja world that ANBU often encounters. This might make him more cynical or, on the contrary, he could try to change ANBU from within. He'd be able to use his Uzumaki powers and his Sage Mode in more covert operations, which would give Konoha a huge advantage. Also, his relationship with other ANBU members would be complex. Some might respect him immediately because of his war hero status, while others might be skeptical of his more open - minded and friendly ways.
One plot twist could be that the person who cheated on Naruto actually has a very good reason, like they were forced to do it to protect Naruto from a greater threat. Another could be that in ANBU, Naruto discovers that the cheating incident was part of a larger conspiracy against him. Maybe his new ANBU teammates turn out to be related to the cheater in some way, creating a lot of internal conflict for Naruto.
In this kind of fanfiction, one possible plot development could be Naruto having to deal with the secrecy aspect of ANBU. He might struggle with the morally grey missions they undertake. For example, he could be sent to spy on an old acquaintance. Naruto, being Naruto, might try to find a more positive solution to the situation rather than blindly following orders.
In some fanfictions, Naruto might join Anbu because of Sakura to prove himself worthy of her. Maybe he thinks that by becoming an elite Anbu member, he can show her that he's strong and reliable.
His relationship with Sasuke would be interesting. Sasuke might be initially suspicious of Naruto's decision to join such a secretive group. But Naruto could convince Sasuke that he's doing it for the greater good of the village and the ninja world, and they could end up working together on some behind - the - scenes missions.
If Naruto joins ANBU after the war in fanfiction, his personality would experience a significant shift. His once boisterous and outgoing nature might be replaced by a more stoic and calculating one. He would need to be more discreet in his actions and words. The trust - building that he was so used to in his normal ninja life would be different in ANBU. He would have to be more guarded about who he trusts, which could make him seem a bit colder on the outside. But deep down, his kind heart would still be there. He'd just be more careful about showing it, as ANBU's world is full of deception and he can't afford to be too naive.
In this kind of fanfiction, Naruto might face some really tough and secretive missions in ANBU. He could be trained in new and deadly ninja techniques. Maybe he would also form some unexpected alliances with other ANBU members, learning from their different skills and experiences.