A popular one is 'Naruto and Greninja: The Elemental Connection'. In this, the author explores how Naruto's elemental chakra and Greninja's abilities interact. It's full of action scenes where they combine their strengths to overcome powerful enemies.
I'd recommend 'Greninja's Hidden Power in Naruto's World'. This fanfiction focuses on Greninja discovering new powers while in Naruto's world. It has an interesting plot where Greninja's powers start to have unexpected effects on the ninja world, leading to a series of exciting adventures.
One great 'Naruto Greninja' fanfiction is 'The Bond of Greninja'. It really delves into the unique relationship between Naruto and Greninja. The story shows how they train together and face challenges side by side, with vivid descriptions of their battles and the growth of their bond.
One idea could be that Greninja, being a ninja - like Pokémon, somehow gets transported to the Naruto universe. It could team up with Naruto and use its water - based attacks in combination with Naruto's Rasengan. Maybe Greninja's ability to blend into the shadows could be used in stealth missions in the Hidden Leaf Village.
There could be unfinished business between them. They might have a shared goal that they haven't achieved yet. Greninja's return to Ash in the fanfiction could be to finally complete that goal, whether it's winning a particular Pokemon tournament or saving a certain place from destruction.
In some fanfictions, Ash Greninja's moment of saving Ash from a dangerous fall during a battle in the Alola region is really cool. It shows their loyalty and quick reflexes.
You can start by looking on fanfiction websites like FanFiction.net or Archive of Our Own. They have a large collection of Pokemon fanfictions, including those featuring Delphox and Greninja. Just use the search function and type in the relevant keywords.
There's also 'Greninja: Shadow of the Swamp'. This fanfic takes place in a spooky swamp setting. Greninja has to face its fears and a new type of enemy. The author does a good job of creating a tense atmosphere throughout the story.
Once upon a time, Greninja was in a deep, dark forest. It was on a quest to find a special crystal that was said to enhance its water - based attacks. As it leaped from tree to tree, it sensed a strange presence. Suddenly, a group of wild Pokémon emerged. Greninja readied itself for battle, its eyes gleaming with determination.
A really cool 'Naruto and Kurama fanfiction' is 'Naruto's True Bond with Kurama'. In this story, Naruto and Kurama communicate on a whole new level, not just about battle strategies but also about their pasts and how they can move forward together. It also has some really nice character development for both of them. For example, Naruto learns more about Kurama's fears and Kurama gets to understand Naruto's dreams better.
I would recommend 'Naruto and Shukaku: A New Alliance'. In this fanfiction, it focuses on a scenario where Naruto and Shukaku have to team up against a new, powerful enemy. It has a lot of action scenes and also some really interesting character development for both of them.
I would recommend 'Naruto's Childhood Redefined'. This fanfiction focuses on Naruto's early years in a different way. It adds some interesting backstories to his relationships with Iruka and the villagers. It's a great read if you want to see a new take on Naruto's past.
One great 'Naruto Shikamaru fanfiction' is 'A Different Path'. It offers a unique take on Shikamaru's character development, showing his growth in ways not fully explored in the original series. The plot is engaging and the author does a wonderful job of staying true to the Naruto universe while adding their own creative twists.