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.
Well, in such a fanfiction, Naruto's character might become more cynical at first. Being cheated on is a huge blow, and it could shatter his trust in relationships. When he joins ANBU, he may focus all his energy on his new duties. He could become more reserved and less of the exuberant Naruto we know. His skills would likely improve rapidly in ANBU, as he pours his heartache into his training. And over time, he might find a new sense of purpose and family within the ANBU ranks, gradually rebuilding his sense of self - worth.
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.
There could be many interpretations in such a fanfiction. Maybe it shows Naruto's vulnerability in relationships. It might be a way to explore his character deeper by putting him in a difficult emotional situation.
Ino could be a very complex character in this fanfiction. It's possible that she cheats on Naruto because she has a fear of commitment. Naruto is a very passionate and all - in kind of person, and that might scare Ino. So, to avoid getting too deep into the relationship, she cheats. Or perhaps there's a power struggle at play. She might think that being with a different person would give her more influence or status in the ninja world. And there could be a hidden agenda that she's following, something that she can't achieve with Naruto but believes she can with someone else.
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, Naruto might face a whole new set of challenges. In the ANBU, he could be pushed to his limits physically and mentally. Maybe he'd use his unique skills in stealthier ways compared to his normal fighting style. Also, his relationships with other ANBU members would be interesting to explore, as he's a bit of an outlier with his loud and brash personality.
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.
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 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.