In the fanfiction where Naruto is Luffy's older brother, what kind of training could Naruto give to Luffy?

They could go on an adventure to find a powerful treasure that combines the power of the One Piece and some kind of ninja - related artifact. Maybe they'd have to fight against a new enemy that is a combination of pirates and rogue ninjas. They might travel to new islands where Naruto's ninjutsu would be useful for exploring hidden caves, and Luffy's stretching ability would help them reach high places or cross large gaps.

Maybe they embark on a journey to save their respective worlds from a common threat. A powerful demon or an evil wizard is trying to destroy both the Naruto universe and the Fairy Tail world. Naruto and Natsu would travel across different dimensions, gathering allies from both worlds. Naruto would use his Rasengan and Natsu his Fire Dragon's Roar to fight off hordes of minions while they search for a way to stop the main villain.

The older brother in the fanfiction might be a character with a tragic past. For example, he could have been experimented on by Orochimaru and gained some strange powers as a result. And he returns to the village later to protect Naruto from the threats that are coming towards him.

One possible character trait is self - sacrifice. He would be willing to put himself in danger for Naruto's sake. He could also be patient. Naruto can be a bit impulsive, so an older brother would need to be patient with him. He might be a bit of an outcast too, like Naruto was in the village. But instead of being shunned for having the Nine - Tails, he could be shunned for some other reason, like having a different ideology about how the ninja world should be run. This would add depth to his character and his relationship with Naruto.

Naruto would probably give Haku training on chakra control. Since Naruto has had to work hard on his own chakra control, he'd be able to pass on some useful tips. For example, he could teach Haku how to better focus his chakra for more precise attacks.

One possible plot could be that Kyuubi protects Naruto from the very beginning. Instead of being seen as a monster, he's Naruto's brother and uses his power to shield Naruto from the villagers' hatred. Maybe they train together in secret, and Naruto becomes much stronger and more confident earlier in the story.

One possible plot could be that Naruto, having grown up in a different world, suddenly discovers he has a sister in Erza's world. He travels to her world to protect her. Along the way, he has to learn about the magic in the Fairy Tail world while also teaching Erza some of his ninja skills. They could face a common enemy that threatens both their worlds, and their combined skills would be crucial in the fight.

It would change a great deal. Naruto being Luffy's older brother would likely introduce new character dynamics. Naruto is from a world of shinobi where secrecy and strategy are important, while Luffy is more about freedom and straightforward action. This could lead to interesting conflicts and resolutions. Maybe Naruto would try to get Luffy to be more cautious at times, which would be a big change for Luffy. Also, the two different power systems, chakra and Devil Fruits, could interact in unique ways that the original storylines of both shows don't cover.

At first, Vegeta might be resistant to having Naruto as an older brother. But Naruto's determination could win him over. Naruto would likely encourage Vegeta to use his power for good. And Vegeta might start to respect Naruto's way of handling things, gradually leading to a closer bond.

Yes, there might be such fanfictions out there. Fanfiction writers often come up with creative crossovers like this. You can try searching on popular fanfiction websites using relevant keywords like 'Naruto Issei older brother' to find them.