There might be a group of anti - Konoha ninjas within Kumo. They see Naruto as a threat not only because he's from Konoha but also because he's becoming so powerful in their own specialty - seal - mastering. So they work together to try and drive Naruto out of Kumo or even harm him to prevent him from getting stronger.
It could be a rogue Kumo ninja who wants to steal Naruto's seal - mastering knowledge for his own evil purposes. Maybe he wants to use the seals to take over Kumo or even the whole ninja world.
Well, it could be about a Naruto who becomes a master of seals in Kumo. Maybe he goes there to learn unique sealing techniques that are different from those in Konoha. He might face challenges from Kumo ninjas who are jealous of his skills or don't trust an outsider mastering their precious arts.
It could be a rogue Kumo ninja who is jealous of Naruto's power and wants to prove himself by defeating Naruto. This ninja might have some dark secrets and a grudge against Kumo as well.
Another possibility is that there is a rogue ninja in Kumo who uses Naruto's neglected state to his advantage. He might try to manipulate Naruto into doing things that would be bad for both Naruto and Kumo, all while remaining in the shadows and making it seem like Naruto is acting on his own accord.
It could be an old enemy of the village who has been waiting for the seal to break. Maybe someone who was imprisoned by the same seal long ago and now wants revenge on the village for sealing them away.
Typically, it would involve Naruto and the concept of a kumo seal master. There might be a focus on unique sealing techniques related to the kumo style. It could also explore the relationships Naruto has with characters who are involved with or knowledgeable about these seals.
Danzo could be a great antagonist in this fanfic. He was always power - hungry and had his own secretive ways. He might see the five pronged seal as a way to control Naruto or to use his power for his own dark purposes. He could try to manipulate Naruto or those around him to keep the seal in place or even make it stronger for his own gain.
Power and growth. Usually, the main character, the kumo seal master, starts from a certain level of skill and grows throughout the story. They face challenges that force them to improve their seal - making and - using abilities.
Well, I'm not sure which specific 'kumo seal master naruto fanfic' is the best. But some popular Naruto fanfic authors might have written something related. You could check out the works of authors who are known for their in - depth knowledge of Naruto lore and unique plotlines. Maybe start with those who have a high number of reviews and followers on the fanfic platforms.
Perhaps an old enemy from Naruto's past who has resurfaced with new and enhanced combat abilities. This enemy holds a grudge against Naruto and the Leaf Village and aims to destroy them both. He has studied Naruto's combat style and found ways to counter it, making him a formidable antagonist.
It could be a rogue ninja who has also mastered some form of insect - based jutsu and wants to use it to take over the Hidden Leaf Village. He sees Naruto as a threat to his plans since Naruto is becoming the master of insects.