There could also be a shift in the power balance within the ninja world. Other villages might see Konoha as weakened due to Minato's self - sealing and might take advantage of the situation, leading to more conflicts and power struggles among the villages.
One possible reason could be to protect the village. Minato is known for his self - sacrificing nature. By sealing himself, he might be containing a great evil or power that could otherwise destroy Konoha. For example, if there was a powerful enemy or a dangerous jutsu gone wrong, sealing himself could be a last - ditch effort to keep everyone safe.
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 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.
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.
Well, it depends on the specific fanfic. Some fanfics might really emphasize Naruto's growth to be on par with Minato in terms of smarts. They could show Naruto learning from Minato's memories or having some sort of spiritual connection that transfers knowledge. However, other fanfics might focus more on other aspects of Naruto's character and not necessarily make him as smart as Minato.
I'm not sure exactly as there could be many different interpretations. It might be about new types of seals in the Naruto universe and how they affect the fate of the characters. Maybe it focuses on a character who discovers a powerful seal that changes the course of their life or the entire ninja world.
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.
Kushina could be an important character even though she's dead in the original story. In this fanfic, her spirit or memories could play a role in Naruto's upbringing. For example, Minato could tell Naruto stories about Kushina's feisty personality and her love for the village.