I'm not sure specifically as I haven't read that particular fanfiction. But it might involve Harry Potter facing six different difficult or painful situations or challenges within the world created by the fanfiction writer.
Perhaps Naruto, after a near - death experience, has a spiritual awakening. He communes with the spirits of the Six Paths and is bestowed with new powers and a new mission. This transformation marks him as the Second Sage of Six Paths, and he uses his new - found wisdom and abilities to unite the shinobi world like never before.
Perhaps a fanfiction where Naruto, as the Sage of Six Paths, has to face a new and powerful enemy that threatens the entire ninja world. He would have to use his newfound powers and wisdom to protect everyone.
In many fanfictions, Naruto as the Sage of Six Paths often has enhanced powers. He can use all six types of chakra natures more proficiently and on a much larger scale. For example, his fire jutsu might be as powerful as a sun's flare, and his water jutsu could create entire oceans. This portrayal gives him an almost god - like status in the fan - created stories, allowing him to face off against extremely powerful foes that he might not be able to in the original series.
Obviously, Naruto is one of the main characters as the story is centered around him being the son of six paths. Sasuke could also be a main character as he has always been Naruto's rival and friend. Their relationship would likely be further explored in this fanfiction.
One possible scenario could be Naruto with his Six Paths powers attending the highschool in the DxD world. He might use his powers in unique ways during the school's supernatural events. For example, his ability to sense chakra could be translated into sensing the different types of magical energies in the DxD school. He could also form interesting friendships or rivalries with the characters from DxD, like Issei. Maybe he'd teach some of them about chakra control in return for learning about their magical abilities.
It could entail Naruto having new and more powerful forms. For example, his Sage Mode could be enhanced with Six Paths chakra, giving him abilities like instant teleportation across great distances or the power to nullify any jutsu with a simple touch.
Another plotline could be centered around Naruto's relationships. His friends and allies might react differently to his new status. Some might be in awe, while others might be a bit jealous or worried. This could create some interesting dynamics and conflicts within the story.
A fanfiction could also be about a prophecy that involves both Naruto and Percy. The Sage of Six Paths had foreseen a future where a great danger would befall both the ninja world and the world of Greek mythology. Naruto and Percy, being the heroes of their respective worlds, must combine their unique skills and powers, including Naruto's Sage of Six Paths powers, to fulfill the prophecy and save both worlds from destruction.