One common theme is the idea of Naruto being in unexpected situations due to crossovers. For example, he might end up in a world from another anime or a different fictional setting. Another theme is the building of relationships with multiple characters, which is the harem aspect. Usually, there's also a focus on Naruto's growth as a character, as he has to adapt to these new and strange situations.
One idea could be Naruto being transported to a different universe where he meets characters from other series in a harem situation. For example, he could end up in a world with characters from Fairy Tail and form relationships with some of the female mages there. Another could be a time - travel plot where Naruto goes back in time and changes events, leading to a different harem dynamic with characters like Hinata, Sakura, and new characters from a crossover world.
One common theme is the exploration of different worlds. Since it's a multi - crossover, there's often Naruto or other characters traveling to different fictional universes. Another theme is the development of the harem relationship. There's usually a focus on how Naruto and the other characters in the harem interact, grow closer, and form emotional bonds.
From the Naruto universe itself, Hinata and Sakura are obvious choices. In a crossover, characters like Erza from Fairy Tail could be included. She is strong - willed and would make an interesting addition to Naruto's harem. Also, Nami from One Piece could be there. Her intelligence and navigational skills would add a different dynamic to the group.
One popular 'naruto multi crossover harem fanfiction' is 'Naruto: The Harem King'. In this story, Naruto finds himself in various crossovers and ends up with a harem of different characters from different universes. It has an interesting plot that combines action and romance well.
Another great one could be 'Naruto: Crossover Chronicles in the Harem'. In this fanfiction, Naruto embarks on a journey that crosses over into different fictional realms and he gathers a diverse harem along the way. The story has a lot of action and the development of relationships is quite engaging.
Sakura is often a likely candidate. She has a long - standing relationship with Naruto in the original series, so it's easy to imagine her in a harem scenario with him.
One popular theme is the development of relationships between Naruto and the multiple characters in the harem. It often focuses on how Naruto's unique personality and abilities attract different individuals.
Power - up is a very common theme. Naruto becomes extremely powerful, often to the point of being godlike. Another theme is the exploration of different universes. Since it's a multi - crossover, he gets to interact with different characters and settings from other fictional worlds.
One interesting concept could be Naruto characters interacting with characters from other popular anime. For example, Naruto meeting Goku from Dragon Ball. It creates unique battle scenarios and character dynamics. Another concept might be Naruto characters in a different fantasy world, like Middle - earth from The Lord of the Rings. They would have to adapt to new cultures and powers.