It could be Orochimaru. Even though he was defeated before, he might come back with a new plan. Maybe he wants to use Naruto and Naruko's family for some dark experiment, like trying to extract the unique chakra combination that their family might have.
Maybe a plot where Naruko comes from a different village and she and Naruto have to deal with the cultural differences in their family. For example, how they raise their children with different values from two different places. They might face some opposition from their respective villages at first, but they work through it for the sake of their family.
Kakashi could also be a character in 'naruto and naruko harem fanfiction'. He can be the mentor figure, guiding Naruto and Naruko through different situations. His wisdom can influence how the harem relationships develop, for example, by giving Naruto advice on how to handle multiple relationships in a proper way.
In this fanfiction, Naruto and Naruko's characters can be developed through their shared experiences. They could face discrimination or special treatment because they are twins. Naruto, who is used to being an outcast, might handle it one way, while Naruko could have a different reaction. This would lead to them growing as individuals and as a pair. They could also develop by learning from each other's mistakes. For instance, if Naruto rushes into a fight, Naruko could teach him the value of planning, and Naruto could show her the importance of believing in oneself no matter what.
At first, it might be a bit awkward. Naruto, not used to being a parent - like figure, would struggle a bit. But as time passes, they would grow closer. Naruto would become someone Naruko could rely on completely.
Well, the plot could be about Naruto creating a clone Naruko for a mission. They could team up to solve puzzles or overcome obstacles in a mysterious dungeon. The focus could be on their combined skills, like Naruto's Rasengan and Naruko's agility, and how they learn to trust and rely on each other during the adventure.
It might develop through shared battles. As Naruto uses his godlike powers in fights, Naruko sees his strength and determination, and she is drawn to him more.
Sakura could be a potential character. She has a long - standing relationship with Naruto, and in this harem scenario, she might be jealous of Naruko at first but then come to accept the situation. Hinata could also be part of it. Given her love for Naruto, she would be an interesting addition to the harem, adding a shy and gentle dynamic.
Sasuke is often paired with Naruko in these fanfictions. Their relationship can be explored in different ways, like they might start as rivals in this alternate universe too, but their bond develops into something more romantic or a deeper friendship. Another common pairing is with Kakashi. He could be her mentor in a more intense and personal way, guiding her not just in ninja skills but also in understanding the complex politics of the ninja world.
No. In the Naruto fanfiction community, stories that involve such disturbing concepts as'slave' are not likely to be popular. Most fans are interested in stories that stay true to the spirit of the original series, focusing on things like character development, epic battles, and the exploration of the ninja world's lore.