One way could be through a magical or technological device. Maybe in the fanfiction, a character discovers an ancient artifact that can open portals between the Naruto universe and the Assassin's Creed Black Flag world. This device could be powered by chakra in the Naruto side and the Pieces of Eden from Assassin's Creed. Characters from both sides would then be able to cross over and interact, leading to all sorts of interesting scenarios like Naruto characters learning the ways of the Assassins or the pirates from Black Flag getting exposed to ninjutsu.
Another possibility is that there is a hidden group in both universes that has been working towards this merge all along. In the Naruto world, it could be a secret clan that has knowledge of other dimensions, and in the Assassin's Creed Black Flag world, it could be a Templar or Assassin off - shoot group. They have been using their respective resources and powers to slowly bring the two worlds together, perhaps for some greater good or for their own secret motives.
The technology aspect can also be a key point. Assassin's Creed has the Animus, which allows people to relive memories. In a fanfiction, this technology could somehow end up in Gotham. Batman, being the detective and tech - savvy hero he is, could study it. He might use it to gain insights into his own past or the history of Gotham, which could be linked to the Assassin's Creed lore. And an Assassin could come to Gotham in search of the Animus, leading to their encounter with Batman.
One possibility could be a story where Naruto is somehow transported to the world of Assassin's Creed Black Flag. He might use his ninja skills to adapt to the pirate - filled environment. For example, his ability to run on water could be seen as a superhuman feat among the pirates and assassins.
The story of Assassin's Creed Black Flag is quite lengthy. You can expect to spend a decent amount of time exploring the game's rich narrative and completing various missions.
Generally, the story of Assassin's Creed Black Flag lasts for approximately 25 hours if you just focus on the main plot. However, if you want to fully experience the game by doing all the side activities and exploring every corner, it can easily extend to 40 or more hours.
The game's story centers on Edward Kenway. He starts as a selfish pirate but gradually becomes involved in the Assassin-Templar war. There's lots of action, mystery, and a richly detailed world to explore.
The story of Assassin's Creed Black Flag follows a pirate-turned-assassin named Edward Kenway. It's set in the Caribbean during the Golden Age of Piracy, filled with adventure, combat, and uncovering ancient secrets.
In Assassin's Creed Black Flag, you play as a pirate who becomes involved in the age-old battle between the Assassins and Templars. The story takes you on adventures across various islands, involving naval battles, exploration, and uncovering hidden treasures and mysteries of the past.
You could also have a character who has a connection to both universes. Maybe a half - Naruto - half - Angeloid being. This character would act as a bridge between the two worlds. They would introduce the concepts of one universe to the other. For example, they could teach the ninja in Naruto's world about the advanced machinery of the Angeloid universe and at the same time show the Angeloid the importance of things like honor and loyalty in the ninja world. As this character moves between the two universes, the two start to blend together more and more.
Naruto might get involved in the naval battles in Assassin's Creed Black Flag. His quick reflexes and strategic mind from being a ninja could give him an edge. He could help the pirates in unexpected ways, like using his shadow clone jutsu to confuse the enemy ships.
A plot could be that Naruto and his friends are transported to the world of Assassin's Creed Black Flag. They team up with the pirates to fight against a common enemy. Maybe the Akatsuki has somehow made an alliance with the Templars, and now Naruto and his crew must use their ninja skills along with the pirates' sailing and combat abilities to take on this powerful alliance. For instance, Naruto could use his shadow clones to board enemy ships while Sasuke uses his Sharingan to anticipate enemy attacks at sea.