Immortality in Naruto - Hellsing fanfiction can bring a whole new level of storytelling. In Naruto, some characters are effectively immortal through means like the tailed beasts' chakra. In Hellsing, vampires are immortal. Combining these, a story could be about a character trying to find a way to end the immortality curse. Maybe Naruto uses his sage mode to understand the nature of vampiric immortality in Hellsing.
One possible crossover in Naruto and Hellsing fanfiction could be the sharing of powers. For example, Naruto's ability to use chakra could be combined with the vampiric powers in Hellsing. Maybe a character from Naruto gets turned into a vampire and has to deal with the new powers and the moral implications in the Hellsing universe.
One possible reason could be fear. Naruto has the Nine - Tails within him, and some in Konoha might be too afraid of its power getting out of control. They may not fully trust Naruto to keep it in check.
One popular theme is the daily life in Konoha. It could be about the characters going about their normal days, training, having fun at the local shops, or just hanging out with friends. Another theme is about Konoha during a war or a major threat. How the village prepares, the strategies they come up with, and how the characters, especially Naruto, contribute to the defense. And then there's the theme of Konoha's past. Stories that explore the history of the village, the founders, and how things have changed over time.
One idea could be a crossover where Naruto is somehow transported to the Hellsing universe and meets Seras. Maybe Naruto's unique powers, like his shadow clones, could be used in battles against the vampires in the Hellsing world. Seras, with her vampire abilities, might initially be seen as an enemy to Naruto but they could end up teaming up.
One interesting Naruto Hellsing werewolf fanfiction could be where Naruto has werewolf - like powers in the Hellsing universe. For example, a story might explore how Naruto's tenacity and his newfound werewolf abilities interact with the dark and vampire - filled world of Hellsing. Maybe he teams up with Alucard to fight a common enemy.
Another reason could be that he witnesses corruption or unfairness within the village leadership. If he sees that the system is rigged against certain groups, including himself or his friends, he could grow to hate Konoha and decide to leave.
Maybe he feels betrayed. In the original story, Naruto has faced a lot of discrimination in Konoha when he was young. So in the fanfiction, it could be that some similar or new issues make him decide to hide.
One possible reason could be feeling betrayed by the village leaders. Maybe they made decisions that Naruto strongly disagreed with, like how they treated certain groups or individuals. If Naruto felt that Konoha was no longer the place that stood for justice and fairness as he once believed, he might abandon it.
Maybe he has some personal grudges against the village. For example, he might have felt betrayed by the village in the past and that made him reluctant to offer help.