One way a Danmachi - Fate fanfiction crossover could function is through the concept of parallel universes. The two universes could be connected in some way, and certain events could cause portals to open between them. In this scenario, the adventurers from Danmachi would enter the Fate world. They would be faced with the complex politics and power struggles there. The Fate characters might view the Danmachi characters as strange new entities. There could be a lot of misunderstandings at first, but as they get to know each other, they could learn from each other's strengths. For example, the Danmachi characters could learn about the strategic use of Command Spells from the Fate characters, while the Fate characters could be impressed by the physical combat skills of the Danmachi adventurers.
Well, in naruto and danmachi fanfiction, a cool crossover could be the jutsu system of Naruto being incorporated into the Danmachi universe. Imagine if Bell had the ability to use Rasengan. It would be a huge power - up for him. Also, the tailed beasts from Naruto could be reimagined as some sort of powerful entities in the Danmachi dungeons, and adventurers would have to figure out a way to either avoid or defeat them.
Definitely Bell Cranel. If he is crossed over into the Naruto world, his growth as an adventurer in Danmachi can be compared to the growth of a ninja in Naruto. His determination to become stronger is similar to Naruto's. Also, Ais Wallenstein is popular. Her combat skills and beauty would make for an interesting combination in the Naruto universe, perhaps having epic battles with Naruto's strong female characters like Tsunade.
In a Naruto - Skullgirls fanfiction, Sakura could team up with one of the Skullgirls. Sakura's medical ninjutsu combined with the brute force of a Skullgirl character would make a formidable duo. They could go on adventures together, facing off against common enemies. It would also be fun to see how the two different art styles blend in the fanfiction, like Naruto's more traditional anime look with the unique, somewhat gothic style of Skullgirls.
One possible scenario in a Naruto - Kaneki fanfiction could be that Kaneki somehow ends up in the Naruto world. Maybe through a strange portal or some sort of jutsu gone wrong. He might initially struggle to adapt to the different environment and the presence of chakra. But his own unique kagune abilities could be seen as a strange new form of power in the Naruto universe.
A Naruto and Albedo fanfiction crossover could be really interesting. They are from different fictional universes, Naruto from the ninja - filled world of Hidden Leaf Village and Albedo from the more fantastical world of Genshin Impact. In this fanfiction, perhaps they could meet through some sort of interdimensional rift. Naruto's skills as a ninja, like his shadow clone jutsu, could be a source of amazement for Albedo, who is more into alchemy and magic in his own world. They could team up to face a common enemy that somehow threatens both of their worlds, learning from each other's unique abilities along the way.
One possible fanfiction could be about Naruto and Kuroka teaming up on a mission. Maybe they are in a world where different anime universes collide. Naruto's skills in combat and his never - give - up attitude could be combined with Kuroka's unique powers to defeat a common enemy.
Well, a really cool concept could be a villain that threatens both the Naruto and DBZ universes. So, characters from both sides have to team up to defeat this powerful foe. Imagine Vegeta and Sasuke having to work together, despite their initial differences. Also, there could be a story where the Dragon Balls are somehow transported to the Naruto world, and Naruto and his friends try to figure out what they are and how to use them.
In this Naruto - Dead Rising fanfiction, Naruto could team up with some of the survivors in the Dead Rising world. They would be initially skeptical of his strange powers but soon realize his value. Naruto could teach them some of his ninja training techniques to help them better defend themselves against the zombies. And in turn, they could teach him about the unique aspects of the Dead Rising world, like how to find and use the best weapons against the undead.
One idea could be that the Tenno from Warframe are summoned to the Naruto universe during a great war. They could use their advanced technology and unique abilities to help the ninja clans. For example, the Excalibur could use his Radial Javelin ability to clear out large groups of enemy ninjas, much like a powerful ninjutsu.