Well, it could be a story where Hana is somehow magically bound to serve Naruto. Maybe she owes him a great debt and has to be his slave as a result. This could lead to various adventures where Naruto has to protect Hana while she's in this subservient role.
Maybe the main antagonist is a dark sorcerer. The sorcerer's goal could be to use Hana's enslavement to Naruto to corrupt Naruto's positive energy. They might believe that by forcing this strange relationship on them, they can turn Naruto towards the dark side. So this sorcerer would constantly try to create more problems between Hana and Naruto.
Definitely not ethical. The Naruto world is rich with different cultures and characters, and reducing a character like Hana to a slave in fanfiction is inappropriate. It not only violates the spirit of the original work but also can create a negative and uncomfortable reading experience for others.
There might be some fanfictions with such a concept, but this is a rather unorthodox and not in line with the positive themes of the original Naruto series. In the original story, Kushina is Naruto's mother, and their relationship is based on family love and the greater Ninja world narrative.
It's likely not one of the most popular concepts. Fanfiction often focuses on more positive relationships or exciting adventures. The idea of one character becoming another's slave has a lot of potential for misinterpretation and might not appeal to a large number of fans. However, there could be a niche group of fans who are interested in exploring the power dynamics and character growth that could come from such a situation.
Hana could be an original character created for this fanfiction. Maybe she is a new ninja in the village who Naruto falls for, but she has a hidden agenda that ends up breaking his heart.
It could have a negative impact. It might make some fans uncomfortable or even angry as it goes against the positive nature of the Naruto series. Many fans love the show for its themes of hope and camaraderie, and this type of fanfiction would be a deviation from that.
In this fanfiction scenario, Hanabi becoming Naruto's slave could also lead to some interesting character development for both. Naruto, who values freedom and friendship, might struggle with having someone in a subservient position to him. Hanabi, on the other hand, might initially resist but then grow to respect Naruto more deeply as she sees his good intentions and the things he can teach her.
In this fanfiction, perhaps there is an evil force that wants to use Anko to get to Naruto. By making Anko Naruto's slave, they hope to manipulate Naruto. But Naruto and Anko end up outsmarting the evil force. Naruto helps Anko regain her freedom and in the process, they both learn important lessons about friendship, trust and the value of freedom. Also, Anko might learn to respect Naruto more and Naruto might see a different side of Anko that he didn't before.
Well, it could be about Kin having some sort of debt or obligation that makes her become Naruto's slave. Maybe she owes him for saving her life in a battle. Then the story might focus on how she has to follow his orders, like helping him with his training or doing tasks around the village for him.