One possible reason could be for Naruto's protection. Maybe she thought by banishing him from a certain place or situation, she could keep him away from a hidden danger that she knew about. For example, there might be a powerful enemy targeting Naruto specifically, and she believed that by making him leave, he would be harder to find.
Some villagers might be in shock. Kushina was an important figure in the village's history, being Naruto's mother. There would be those who would question Naruto's decision and lose faith in him. They might start to fear for their own safety, thinking that if someone like Kushina could be banished, they could be next.
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.
Perhaps Naruto was falsely accused of something really serious in the fanfiction. Like he was thought to be involved with the enemy in some way. Kushina, being in a position of power, had to banish him to maintain the order and trust within the village, even if she didn't truly believe he was guilty.
One possible reason could be a misunderstanding. Maybe some false information was spread about Kushina being a threat to the village, and Naruto, in his role as Hokage or a powerful figure, felt he had no choice but to banish her to protect the village. Another reason might be related to some sort of dark influence or curse that made Naruto act out of character and banish her.
At first, Naruto might be extremely confused. He has always considered the village his home and Kushina as someone important. So being banished by her would leave him feeling lost and not understanding why it happened.
One popular 'banished Naruto x Kushina' fanfiction might be 'Naruto's Redemption with Kushina'. In it, Naruto, after being banished, meets Kushina in a unique way. Maybe she has been brought back somehow. Their relationship then develops as they both have to face the challenges of a world that has shunned Naruto. It shows their bond growing stronger in the face of adversity.
Another aspect could be that the fanfiction delves into how Kushina's presence affects Naruto's relationships with others. For instance, his relationship with Sasuke could be different. With a strong maternal figure in his life, Naruto might be more stable emotionally and be able to approach Sasuke in a more understanding way, which could potentially change the whole dynamic of their rivalry and friendship.
Well, often it starts with Naruto in a vulnerable state after being banished. Kushina, either through some magical means or just chance, enters his life. Their relationship might begin with Kushina showing kindness to Naruto when no one else does. This kindness then blossoms into a deeper connection as they share their stories and feelings.