In the fanfiction, Naruto's enemies' reactions could vary greatly. For instance, Orochimaru might see it as a chance to conduct more experiments on Naruto or the tailed beast. The Akatsuki, on the other hand, might change their plans completely. They were after the tailed beasts, and now that Naruto has revealed his, they might either try to capture him right away or come up with a more elaborate plan. And then there are smaller enemies who might just cower in fear at the thought of facing a jinchuriki like Naruto who has openly shown his power.
Well, one possibility is that his friends might be initially shocked. But then they would likely accept him and vow to protect his secret. After all, they've been through a lot together already.
The Joker might be furious. His identity has been his biggest secret and Batman taking that away is like stripping him of his power. He could go on a wild rampage, more so than usual, targeting Batman directly and also anyone who he thinks might have had a part in the revelation.
Kakashi could be involved too. Given that Kakashi has trained Naruto and seen his growth, Naruto might trust him with his secrets. He could reveal his thoughts on how he wants to change the ninja world for the better and the steps he is planning to take in the future.
He might become more wild and instinctive. Tailed beasts are known for their raw power and basic instincts. So Naruto could be more impulsive, acting on his first thoughts rather than thinking things through. For example, in a fight, he might not hold back as much as he usually does as a normal ninja.
They would probably be shocked. Since Naruto is such an important figure to them, any big secret would likely cause a stir. For example, if it's about his Nine - Tails secret, they might be initially stunned as they realize how much he has been carrying alone.
One interesting fanfiction could be where Naruto has an unexpected and more powerful tailed beast transformation during a major battle. Maybe he combines the power of all the tailed beasts in a new way, surprising his enemies and allies alike.
Perhaps he reveals his dreams for the future of the Hidden Leaf Village that are more personal and not part of his official Hokage - related goals. For example, he might talk about his hopes for how the different ninja clans interact and co - exist in a more harmonious way, something that he has been thinking about but hasn't shared with the group yet.
In this kind of fanfiction, Naruto might initially be shocked. He would probably have to re - evaluate his whole identity. He has always seen himself as a ninja, but finding out he's a tailed beast would make him question his place in the ninja world. He might struggle with the idea that he is not just a human with a special power, but is in fact a tailed beast. This could lead to some interesting character development as he tries to come to terms with this new reality.
Naruto could also be a bit angry at first. Angry that she had been away from him all this time. But then that anger would quickly turn into overwhelming love and relief. He would have so many questions to ask her about why she wasn't there as he was growing up, but at the same time, he would be so glad to have her there now.
His relationships with his friends would become more complex. His friends might be a bit scared or at least unsure about this new side of him. For example, Sakura might be worried about how to approach him now. Sasuke, on the other hand, might see Naruto in a completely different light, either as a threat or as an even more interesting rival. His relationship with the village elders would also be different. They might try to keep a closer eye on him or even isolate him to some extent.