In addition to his close friends, other characters from the guild could also play a role. Maybe the master of the guild, Makarov, would have some words of wisdom for Natsu upon his return. And there could be some side characters who were affected by the war in some way and now look up to Natsu. For example, some of the younger members of the guild who see Natsu as a hero. Also, there could be antagonists who see Natsu's return as an opportunity to test their strength against him or cause trouble for him and his friends.
Obviously, Natsu himself is the central character. His friends like Lucy, Gray, and Erza are likely to be involved. They would be the ones to welcome him back and also be part of his new adventures or challenges that come after his return.
There could be new characters introduced as well. For instance, someone Natsu met during the war, either an ally or an enemy. If it was an ally, this new character could join Natsu's side in his post - war activities. If it was an enemy, they might come seeking revenge. And then there are the characters from other guilds or factions that might be interested in Natsu's new skills or the information he brought back from the war.
The fanfiction could start with Natsu's grand return. His friends are overjoyed but soon realize he's different. He might be haunted by the memories of the war. Maybe he lost some dear friends during the war and is now more determined to protect the ones he still has. His return could also trigger some rivalries. There could be those who are jealous of the newfound respect he has earned from the war, or those who think he has become too powerful and might be a threat. This would create a lot of drama and new storylines in the fanfiction.
Maybe it's an old enemy who survived the war and has grown stronger. They hold a grudge against Natsu and his friends and are now seeking revenge. For example, if there was an enemy that was thought to be defeated before the war but managed to survive and is now back with a vengeance.
His close friends like Lucy would be extremely happy. They might cry tears of joy and immediately hug him. Gray, on the other hand, might act cool at first but then show his true happiness. Erza would probably be the most composed but still show her delight through a warm smile.
Gray would be one of the main characters to interact with Natsu. Their friendly rivalry is well - known in Fairy Tail. Makarov, as the guild master, would also have an important role in interacting with Natsu. He might give Natsu some important tasks or just have a grandfatherly chat with him about his return.
Most likely, the other members of Fairy Tail would be involved. For example, Lucy might be there. She could be in distress during the attack that Natsu is trying to fend off, or she could be one of the first to find Natsu after he has fallen. Gray could also be involved, perhaps he was fighting alongside Natsu or arrives shortly after to see what has happened. Erza too, as a strong and important member of the guild, she may play a role in the events following Natsu's fall.
Obviously Naruto himself. Then Sasuke would probably be involved as they have a deep connection. Sakura too, since she's part of their team. Kakashi might also play a role as Naruto's former teacher.
Natsu's friends like Gray, Erza, and Lucy are often involved. Gray might be constantly teasing Natsu about the transformation, creating some funny banter between them. Erza could be the one who tries to keep order and protect Natsu in this new form. Lucy might offer more emotional support, sharing girl - related experiences with Natsu to help her adjust.
One possible plot could be that Natsu returns with newfound powers. He might use these powers to help rebuild the world after the war, and also to reunite with his friends. Maybe he has to face some remnants of the enemy forces that still lurk in the shadows.
Another possibility is that Ash returns with some sort of special mission or knowledge from the war. He might be on a quest to use this new - found knowledge to make changes in his homeland. He could face opposition from those who don't believe in his ideas or are afraid of the changes he wants to bring. This could lead to a story full of adventure and self - discovery.
Gray is another character. His ice - magic can complement Natsu's fire - magic. They might team up to fight enemies or overcome obstacles in the way of saving Fairy Tail. Sometimes they bicker while doing so, which adds some humor to the story.