A fascinating plot aspect in such fanfiction is the idea of the Holy Grail War in the Naruto universe. Picture the ninja villages competing for the Grail. The characters from Naruto would have to form alliances and strategies similar to what happens in Fate Stay Night. Also, the concept of summoning Servants in the Naruto world. What if Naruto or Sasuke could summon a powerful Servant? How would they interact? And how would the Servant adapt to the ninja world? These are all really interesting plot elements.
One interesting plot idea could be that the Servants from Fate Stay Night end up in the Naruto world. For example, Saber could team up with Naruto. Saber's noble and just nature would blend well with Naruto's determination to protect his village. They could face off against common enemies like Orochimaru, who might be interested in the power of the Servants. Another idea is that the concept of chakra in the Naruto world could interact with the magic in Fate Stay Night. Maybe a mage from the Fate universe tries to study chakra and finds a way to combine it with their own magic system, creating a whole new type of power. A third plot could involve the Holy Grail War taking place in the Hidden Leaf Village. The ninjas would be both intrigued and cautious about this strange new event, and the Servants would have to navigate the politics and unique environment of the village while fighting for the Grail.
The concept of Naruto being a Master in the Fate/stay night world is also very engaging. He could summon Servants and form unique partnerships. His understanding of loyalty and friendship from the Naruto world would influence how he interacts with his Servant. It often leads to heartwarming and action - packed storylines.
A plot could be that Mordred is summoned by a powerful ninja as a last - ditch effort to fight against an ancient evil that has emerged in the Naruto world. This evil has powers similar to some of the powerful Servants in Fate Stay Night, so Mordred's expertise is needed.
Well, perhaps in this crossover fanfiction, the power systems of both could merge. For example, the magical abilities of the Fate Stay Night characters could combine with the Freezing characters' abilities. Let's say Saber's Excalibur could be enhanced by the energy manipulation skills of a Freezing character. And there could be a love triangle between a Fate Stay Night male character, a Freezing female character, and another character from either universe, which adds a lot of drama to the story.
In a Fate Stay Night Skyrim crossover, Archer could be summoned by a powerful mage in Skyrim. Archer would find the concept of the Thu'um fascinating as it's a form of magic he's never encountered. He could start exploring Skyrim, looking for ways to use his own abilities in conjunction with the local magic. He might get involved in the civil war between the Stormcloaks and the Imperials. His strategic mind could help whichever side he decides to side with. And when the dragons return, he could use his Unlimited Blade Works to create weapons specifically designed to fight dragons, like blades that can pierce dragon scales more easily.
Personally, I think the development of the relationship between Shirou and Saber is one of the most interesting plots. Their different outlooks on life and values gradually change as they interact more. Also, the battles in the Holy Grail War, like the ones where the Servants use their unique abilities, are really exciting and add to the overall appeal of the story in the Fate Stay Night Novel.
I'm not entirely sure as it could cover a wide range of things. It might be a fan - made story that combines elements from Naruto and Fate Stay Night in a rather strange or comical ('troll') way. Maybe it has Naruto characters in the Fate Stay Night world dealing with magic and the Holy Grail War in unexpected ways.
One common theme is the power struggle. Both Naruto and Fate Stay Night have characters with different levels of power, and in fanfiction, often there are stories about characters trying to gain more power or deal with the power they have. For example, Naruto characters might have to adapt to the magic - based power system in Fate Stay Night.
The plot might involve Naruto being summoned to the Fate Stay Night world by accident. There, he catches the attention of Fem Gilgamesh. She could be intrigued by his unique chakra and his ability to keep getting back up no matter how many times he is knocked down. They might then embark on a journey to find a way to send Naruto back home. Along the way, they face various challenges and enemies. Naruto could teach Fem Gilgamesh about the value of friendship and hard work, which are concepts not as emphasized in her world, while she could introduce Naruto to the complex magic and power hierarchies of the Fate world.
One interesting Fate Stay Night Naruto fanfic is 'Naruto in the World of Fate'. In this fic, Naruto is somehow transported to the Fate Stay Night universe. It's really cool to see how his ninja skills interact with the magic and combat system in the Fate world. Another one could be 'Fate Servants in Konoha' which imagines what would happen if Fate's Servants showed up in Naruto's village.