In some versions of fanfiction, Naruto might use a new and powerful sealing jutsu that he has either created or learned specifically for this purpose. It could be a jutsu that combines his Uzumaki heritage's sealing knowledge with his own unique chakra control.
One consequence could be that Naruto has a constant struggle to keep Kaguya's power in check. He might experience internal battles within his mind as Kaguya tries to break free.
One possible plot development could be that the village is in great danger from an enemy too powerful to defeat directly. Naruto, seeing no other way, seals himself away to act as a last - line - of - defense deterrent. If the enemy tries to completely destroy the village, Naruto's sealed power could be unleashed to counter them.
It could be a new and extremely powerful ninja from a far - off land who has a vendetta against Konoha. His power might be so great that Naruto decides the only way to stop him in the long run is to seal himself away as a sort of trap for when the antagonist gets too close to achieving his goals.
There is a possibility that it was an ex - shinobi who had retired from active duty. This person had amassed a collection of seals during their career and now made a living by selling them to other ninjas like Naruto.
Well, Naruto could change Kaguya in the fanfiction by introducing her to the concept of redemption. Given his own journey of facing his inner demons and coming out stronger, he might convince Kaguya that she can atone for her past sins. He may take her on a journey through the ninja world, showing her how people have rebuilt and thrived despite the chaos she once caused. This could make her re - evaluate her actions and change her perspective on the world and her place in it.
Well, considering Naruto's own experiences and the variety of seals in the Naruto universe, he could sell communication seals. These would allow ninjas to send messages over long distances. He might also sell seals that are related to elemental jutsu, perhaps ones that enhance or modify fire, water, wind, earth or lightning techniques.
Perhaps Naruto was in a situation where he had made a deal. For example, he promised to pay for the seals in exchange for some information about a missing nin or a secret technique. He values knowledge and power, and if paying for the seals was part of getting closer to achieving his goals, he would do it.
Yes, there are likely some fanfictions that explore a special connection between Naruto and Kaguya. In some fanfictions, authors might create scenarios where Naruto, due to his unique abilities and kind - hearted nature, manages to reach out to Kaguya in a way others couldn't. This could involve him understanding her past and trying to bring some form of redemption or peace to her.
In the fanfiction, Naruto could enter Kaguya's mind. He might discover her past traumas that led her to become so power - hungry and vengeful. By understanding her pain, Naruto could offer her forgiveness and a new path. He could show her a vision of a future where she is part of a united world, not feared or hated, but respected and loved if she changes her ways. This could be a powerful incentive for Kaguya to change.