Obviously Naruto would be the most important character as the story revolves around him controlling spirits.
Sasuke could also be an important character. He might be initially skeptical of Naruto's new power or even see it as a threat at first. But later, they could team up, with Sasuke's skills complementing Naruto's spirit - controlling ability.
There could be some original characters introduced as the spirits that Naruto controls. For example, a powerful spirit of an ancient ninja who has a lot of wisdom and helps Naruto understand his power better. Also, Kakashi could play an important role as Naruto's mentor, guiding him on how to use this new and potentially dangerous power without losing himself.
Well, it could be about Naruto having the unique ability to control various spirits. Maybe he discovers this power during a difficult mission and has to learn to master it quickly to defeat a powerful enemy.
Obviously, Naruto Uzumaki himself is the central character. His wife, Hinata, is also very important as she is part of his family and would play a major role in family - related storylines, like raising their children.
The important characters in 'Naruto Returns to the Village Fanfic' would surely include Naruto. Then there are his closest friends and allies. Hinata could be there, and their relationship might be further explored. The elders of the village could also be important as they might have different reactions to Naruto's return. Some might be welcoming, while others might be skeptical. And the new generation of shinobi, like Boruto's friends if it's set in that time frame, could look up to Naruto and be influenced by his return.
In a 'naruto after pain fanfic', Naruto is key. However, characters like Tsunade are important too. She can lead the medical and administrative aspects of the village's recovery. Then there are Naruto's friends like Kiba and Choji. They can help with the physical tasks of rebuilding, and also in the security patrols around the village to prevent any new threats.
Naruto is the central character, no doubt. Hinata could be important as well. If Naruto sees a future related to his family or his relationship with Hinata, she will play a significant role. Additionally, the Hokage, like Tsunade or whoever is in charge at that time, would be important as Naruto may need to report the future he saw to the village leadership to take collective action.
Sasuke is likely to be an important character. His power and his relationship with Naruto could play a big part in the story. He might help Naruto in the fight against the Juubi or have some other role related to the sealing process.
The important characters would start with Naruto. Then, any of the other Jinchuuriki that the author decides to include. For example, if the story is set in a certain time period, we might see the Jinchuuriki from Naruto's generation more prominently. So, characters like Gaara and Killer Bee would be very important. And there could be some new or less - known Jinchuuriki introduced to add more depth and variety to the story.
Obviously, Naruto himself is the most important. But his friends like Sasuke would also play a significant role. Sasuke could be Naruto's right - hand man, helping him with security and intelligence matters in the village.
Another character could be the Nine - Tailed Fox. Kushina was once the jinchuriki of the Nine - Tailed Fox. When Naruto meets his mother, the topic of the Nine - Tailed Fox might come up. Maybe Kushina could tell Naruto some secrets about controlling the Nine - Tailed Fox's power that she learned during her time as its jinchuriki.
Obviously Naruto is one of the most important. His strength and his ability to inspire others are crucial in the Fourth War setting. He's the one who can turn the tides with his positive attitude and powerful jutsu.