Often, the main antagonists can be the village elders or some corrupt shinobi within the village who are behind their banishment. These characters may fear Naruto and Naruko's growing power and influence.
One possible plot could be Naruto and Naruko being banished unjustly and then having to prove their worth outside the village. They might encounter new allies and enemies, and develop new jutsu in the process.
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.
Naruto might also initially feel a sense of abandonment. However, his kind - hearted nature could lead him to try and see the good in the situation. He could start to explore the world outside, learning about different cultures and ninja techniques. He may use this experience to become more empathetic towards others who have also faced hardships, and in the long run, this banishment could be a turning point in his life to become an even greater ninja.
At first, Naruto is probably shocked and confused. He might not understand why the village would take such a harsh step just for hurting Sasuke. He may feel betrayed, especially if he thought he had friends and allies in the village.
A possible plot for this type of fanfiction could involve the banished ninja having a secret mission that the village doesn't want to be associated with. So, they banish the ninja to make it seem like they have no part in it. The ninja then has to complete the mission while also dealing with the stigma of being banished.
Well, in a fanfiction like this, it could explore Naruto's sage mode abilities in a new context while he's with Yugito who has also been banished. Maybe they form an alliance to fight against the forces that banished them. They could discover new powers together and change the shinobi world's view of them.