The worlds might merge due to a common enemy. For example, an ancient evil that exists in both the Naruto universe and Bayonetta's world starts to gain power. To stop it, the barriers between the two worlds begin to break down. As a result, Naruto's village, Konoha, could end up in Bayonetta's city - like setting. The shinobi would have to adapt to the new environment filled with witches and demons, and Bayonetta could learn from the ninja's teamwork and strategies.
Their worlds could merge through a magical portal. Maybe a powerful jutsu in Naruto's world accidentally creates a rift that connects to Bayonetta's dimension. This would allow characters from both sides to interact.
In a Naruto Bayonetta fanfic, their worlds could merge in a more spiritual way. There could be a prophecy in both worlds that foretells the coming together of two powerful forces. Naruto, with his strong chakra, and Bayonetta, with her magical abilities, are the keys to this merger. Their combined power could create a new realm that combines the best of both worlds. The forests and mountains of Naruto's world could blend with the gothic architecture of Bayonetta's world. And the people from both sides would have to learn to coexist, with the ninjas sharing their combat skills and the witches sharing their magic knowledge.
In a fanfic, the merging could also be due to a common threat. Suppose there is a dark force that wants to conquer both the ninja world and the vampire world. To fight this threat, Naruto and Moka's worlds start to merge gradually. This would result in unique alliances. For example, ninja and vampires might have to work together, with Naruto and Moka leading the way. They would need to find a way to combine their different fighting styles and powers, like Naruto's shadow clones and Moka's blood-based attacks.
In a Naruto and Batman crossover fanfiction, their worlds could merge in a few ways. One way could be through a portal. Maybe some sort of evil magic or advanced technology creates a portal between Konoha and Gotham. This would bring Naruto and his friends into Batman's world, or vice versa. Another possibility is that a powerful villain has the ability to manipulate space - time and decides to bring the two worlds together for his own evil purposes.
In a merged world, the power structures would change. The Gems, who are used to being the protectors of Earth in their world, would now have to share that role with Ben. Ben's aliens could provide new ways to defend the planet, while the Gems' magic could offer solutions to problems that Ben's aliens couldn't handle alone. Also, the villains from both worlds might team up, forcing Ben and Steven to form a united front. They would need to combine their powers, like Ben using an alien form that could enhance Steven's powers, or Steven using his powers to boost an alien's abilities.
The worlds could merge through a mysterious portal. This portal could be created by some powerful jutsu in Naruto's world that goes wrong or by an experiment in Build's world. Once the worlds start to merge, the characters would be in for a shock. The ninjas in Naruto's world would see the advanced technology of Build's world, and the people in Build's world would be amazed by the use of chakra.
Their worlds could merge in a lot of ways. For instance, the technology from the Avengers' world could be introduced to Lilo and Stitch's Hawaiian setting. Maybe Stark Industries could set up a research facility in Hawaii to study Stitch's biology. And in return, Lilo could introduce the Avengers to the local culture and the concept of 'ohana', which could strengthen the Avengers' sense of family within the team.
The merge can also happen on a more conceptual level. For example, the idea of friendship and teamwork, which are important in both series, could be the connection. Naruto's belief in his friends and the Digidestined's bond with their Digimon could be seen as similar. This similarity could be the starting point for the two worlds to interact in fanfiction. Writers might have Naruto and the Digidestined team up to fight a common enemy that threatens both the Digital World and the ninja world. They would combine their unique powers and skills to achieve victory.
One way their worlds could merge is through a shared mystery. Maybe there's a strange case in the Naruto world that requires Sherlock's deductive skills. For example, a series of disappearances in Konoha that seem to have no pattern. Sherlock, using his keen observation, could notice small details that the ninja miss. Naruto, on the other hand, with his knowledge of the ninja world and its secrets, could provide context that Sherlock needs to solve the mystery. Their different abilities would complement each other, leading to an interesting crossover story.
Well, in a popular one called 'Naruto's New Realm', Naruto discovers a portal that leads to Rias's world. As he steps through, the two worlds begin to merge in a way that combines the ninja techniques with the demonic powers of Rias's realm. It's really cool to see how the two different power systems interact and how the characters from both sides deal with the new situation.
In fanfiction, the merge could happen because of a powerful jutsu gone wrong. This jutsu could distort space - time and connect the two universes. In the merged world, the Gundam pilots would have to deal with the threat of ninja attacks. They could use their Gundam building skills to create mechas that are better equipped to handle ninja abilities like genjutsu. Meanwhile, the Naruto characters would be fascinated by the Gundam battles and might try to participate using their own combat skills.
The merging could also happen due to a powerful artifact. Suppose there is an ancient artifact in Skyrim that has the power to connect different realms. If it gets activated, it could pull the world of Game of Thrones into Skyrim's universe. Then, the political intrigue of Game of Thrones, like the power struggles in King's Landing, could be introduced to Skyrim's cities. The Nords in Skyrim would have to deal with the complex politics of the Seven Kingdoms.