A great One Piece fanfiction should have engaging characters. Whether it's new characters added to the story or a deeper exploration of the existing ones. For instance, if it focuses on Sanji's backstory in a more detailed way, it can be really interesting. And the world - building should be consistent with the One Piece universe, with the same kind of islands and mysteries.
The popularity of both 'One Piece' and 'Naruto' is a big factor. Fans of these shows love to see new interpretations and crossovers. The unique powers in each series, like the Sharingan in 'Naruto' and Devil Fruits in 'One Piece', are exciting to combine in fanfics.
The unique aspect is that it combines the familiar characters of One Piece with the concept of reaction. It's fun to see how characters like Luffy or Zoro would react to things they might not have known before, like modern technology or different interpretations of their own stories.
Well, One Piece Monet fanfic often delves into uncharted areas of the One Piece world. For example, it can show Monet in different alliances or situations that the original story didn't cover. It also allows fans to explore her relationships with other characters in new and exciting ways. Maybe she forms an unexpected friendship or rivalry. All these possibilities make the fanfic really engaging.
Nami is special in the One Piece novel because of her unique skill set. As a navigator, she is essential for the Straw Hat crew's voyages. Without her, they would be lost at sea.
The character of Katakuri himself is very appealing. He has a complex personality and strong powers. Fanfiction allows writers to explore more of his backstory, like his relationship with his family, which was only briefly touched upon in the original One Piece. So, it gives a chance to dig deeper.
The main thing that makes it unique is the gender - swap of Luffy. This simple change can lead to a whole new set of character dynamics. For example, the interactions with male characters like Usopp or Franky will be different. Also, the way she is perceived by other characters in the One Piece universe will be distinct. Enemies might underestimate her because she is female, but she'll prove them wrong with her strength.