One great 'Naruto x Ninja Gaiden' fanfiction is 'The Ninja Alliance'. It combines the unique ninja skills from both universes in an exciting way. The story follows Naruto as he teams up with Ryu Hayabusa to face a new, powerful enemy that threatens both their worlds. The fight scenes are well - written, making it a thrilling read.
One idea could be exploring the untold adventures of the next generation in the Naruto world. Maybe focus on how the children of the main characters deal with new threats that are emerging. For example, they could face a new group of rogue ninjas who have a different set of jutsus.
Boruto is an obvious choice. He and Sarada have a unique friendship in the Naruto universe, and their interactions can add a lot of depth to the story. They could go on missions together or have friendly competitions.
Another plot could involve Sarada going on a journey to find out more about her father, Sasuke. She could encounter people who knew Sasuke in his younger days and learn about his past misdeeds and heroic deeds, which would shape her understanding of him and herself as his daughter.
A common plot in such fanfiction is Sasuke and Sakura's relationship being tested. For example, rumors start spreading in the village about Sasuke's loyalty again. Sakura has to defend him while also dealing with her own doubts. Or perhaps there's a plot where a powerful ninja from another village falls in love with Sakura. Sasuke then has to show his love for Sakura in a more obvious way to keep her by his side. This can lead to some really interesting character development and relationship - building moments.
One idea could be exploring the untold adventures of Naruto's father, Minato, during his own ninja days. Maybe his secret missions and how he met Naruto's mother.
Naruto himself is always popular. Writers can explore different aspects of his life, like his training in more detail or his relationships with other characters in new situations.
A really cool plot could be that Orochimaru somehow manages to open a portal to the Ninja Gaiden world. He starts experimenting with the creatures and powers there. Naruto and his friends have to enter this new world to stop Orochimaru, and they meet characters from Ninja Gaiden who help or hinder them along the way.
Sakura's medical ninjutsu could be used to heal the wounds that characters from Ninja Gaiden might sustain in battles in the Naruto universe. In return, characters like Ryu could teach Sakura some of their more intense physical combat techniques, enhancing her close - range fighting abilities.
There could be a group of orphans who have banded together and developed their own unique style of ninjutsu out of necessity. These orphans could add a new dimension to the story as they struggle to survive in a world full of powerful ninjas while also trying to find their place in it.