Naruto might become more cautious. After being kidnapped, he realizes the world is more dangerous than he thought. He could start to be less impulsive and think more before acting.
One possible plot development could be that Naruto's friends in Konoha realize he's missing and start a search mission. They might suspect Kumo immediately due to the history of tensions between the two villages. Meanwhile, in Kumo, Naruto could be held in a secret location. Some in Kumo might want to use him as a bargaining chip against Konoha, while others might see his potential and try to turn him into an asset for Kumo.
Maybe in the fanfiction, Naruto neglected Kumo because he was too focused on his own village's problems. But then something major happens in Kumo, like a powerful enemy targets them. Naruto realizes his mistake and goes to Kumo to make amends. He teams up with the Kumo shinobi, and they work together to fend off the threat. Along the way, he learns about Kumo's unique culture and forms strong bonds with their ninja.
One possible plot could be that Naruto goes to Kumo but is not well - received there. Maybe the people of Kumo are still suspicious of him because of his status as a Jinchuuriki. They could isolate him, and Naruto has to struggle to prove himself worthy of their trust. He might also face discrimination from some of the Kumo ninja.
If Naruto is kidnapped by Kumo in fanfiction, it could lead to a series of intense battles. Naruto himself might try to escape on his own using his ninja skills and the power of the Nine - Tails. His captors in Kumo would probably want to extract some sort of information from him, like the secrets of the Nine - Tails or Konoha's defense strategies. However, Naruto is a tough character and would surely put up a fight.
The Kumo ninja would likely be angry at first. They'd feel that Naruto, as a symbol of hope in the shinobi world, should have noticed their problems. But some of them might also be hopeful that Naruto's arrival would finally change things for the better. As for Naruto himself, he'd probably be shocked to realize how much he'd overlooked Kumo and would feel a sense of guilt.
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.
Naruto could try to befriend some of the Kumo ninjas who might not be in favor of the kidnapping. By winning them over, they could help him escape. Also, he could use his knowledge of ninja techniques and his quick thinking. For example, he could use substitution jutsu to switch places with an object when the guards are not looking and then make a run for it.
It could be that Kumo has a rogue group within their village that wants to use Naruto for their own malicious purposes. They kidnap him in the chaos of a diplomatic visit or something similar. Once kidnapped, Naruto finds himself in a difficult situation as he is far from home. But he uses his never - give - up attitude and starts making friends with some sympathetic Kumo ninjas who help him in his fight against the rogues and eventually his escape back to Konoha.
Well, one possibility is that Naruto could quickly rise through the ranks in Kumo. Since he was neglected at home, he might be more determined to prove himself there. He could form strong bonds with new friends and comrades in Kumo who actually value him, which would be a huge change from his situation in his original village.