It might make Percy more confident. With the trident, he has a powerful symbol of his father's support. He could use it to face stronger enemies and gain more respect in the demigod world.
The trident might represent Percy's growth. It could mean that he has reached a new level in his development as a demigod, and Poseidon is acknowledging that with this gift. It's like a rite of passage in a way.
Well, perhaps the plot could involve Percy being given the tail as a sign of special favor from Poseidon. He might then have to learn how to use the tail in underwater adventures, like swimming faster or having better control in the ocean currents. It could also lead to him being able to communicate more effectively with sea creatures, since he now has a more 'aquatic' form.
Naruto might initially struggle with the power of the Trident. Since he's used to his chakra system, the magic or divine power of the Trident would be something new. He could start by accidentally activating some of its basic powers, like creating small whirlpools or summoning small sea creatures. As he spends more time with it, he would learn to control it better, maybe even combining his own ninja techniques with the Trident's power, like using the Rasengan while channeling the Trident's energy through it.
In some fanfictions, Percy might obtain the trident through a special quest. Maybe he has to prove himself worthy to an ancient sea deity who then bestows the trident upon him as a symbol of power and trust.
His character could change in several ways. He would have a new sense of identity. No longer just a demigod with powers, but now something more 'aquatic'. He might be more curious about his father's world and want to spend more time there. This could lead to some conflict with his human side, as he has to balance his life on land and his new underwater existence. Also, he could become more of a leader among the sea creatures, as he has a unique connection to them through the tail.
Well, it could be that Poseidon's Trident has been stolen and Naruto is called upon to find it. He teams up with some of Poseidon's loyal servants or maybe even a mermaid or two. Along the way, he uses his ninja skills to track down the thieves. When he finally finds the Trident, he has to face the main villain who stole it. Naruto might use his Rasengan in combination with the power of the Trident to defeat the bad guy and return the Trident to Poseidon.
Well, if Naruto had Poseidon's trident, it would completely change the power dynamics in the Naruto universe. Firstly, the trident is a symbol of great power in Greek mythology. Naruto could use it to control water in ways that are unimaginable in the Naruto world. He might be able to create massive tidal waves to defend Konoha or use water to enhance his already existing jutsus. Also, it could potentially give him an edge in battles against powerful foes like Madara or Kaguya. With the trident, Naruto could become an even greater protector of his village and the entire ninja world.
In fanfictions, Poseidon often interacts with baby Percy in a very gentle and protective way. He might use his powers to create a safe environment for Percy, like a special underwater grotto where Percy can be hidden from danger. Sometimes, he sends sea creatures to watch over Percy, like dolphins or friendly sea nymphs.
Annabeth would definitely be involved. As Percy's girlfriend, she is often by his side during his adventures. She could be the one who witnesses Poseidon's pride towards Percy and helps Percy understand the significance of it. Grover, Percy's best friend, is also likely to be there. He might provide some comical relief during the serious moments when Poseidon is showing his pride. Also, other demigods from Camp Half - Blood like Jason, Piper, and Leo could be involved. They could be in awe of Percy's new - found status with Poseidon and might interact with him differently because of it.