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.
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.
Maybe Natsu comes back with new powers. He might have to face old enemies that have grown stronger in his absence. Also, his relationships with his friends could have changed, and he'd have to work on rebuilding those bonds.
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.
Well, one possible plot twist could be that Natsu returns with a new, super - powerful form that no one expected. Maybe he has mastered a long - lost magic during his absence.
One possible plot development could be that Natsu discovers a new and powerful magic during his return that gives him an edge in saving Fairy Tail. Maybe he finds a way to combine his Fire Dragon Slayer magic with some ancient magic he stumbles upon on his journey back.
One possible reason for Natsu to return badly hurt in a fanfiction could be a very tough battle. Maybe he faced an extremely powerful enemy that was far beyond his initial expectations. For example, if he encountered a new type of dark mage with some unknown and dangerous magic. This could lead to him getting seriously injured and having to struggle to return.
The plot could be that the dragon's return disrupts the current peace in Natsu's world. Maybe the dragon has some unfinished business with an old enemy, and now that he's back, he drags Natsu into it. Natsu, being loyal to his foster father, follows him into this new conflict. This could involve a lot of action - packed battles and some emotional moments as Natsu has to deal with the potential danger to his foster father.
In the 'natsu went mia in war fanfiction', Natsu is presumably a central or important character. He could be a hero - type figure who was expected to play a significant role in the war. It's possible that he has some special abilities or traits that made his presence crucial. Since he went MIA, the whole story might be about his friends or allies trying to find him or dealing with the aftermath of his disappearance. It could also be that Natsu is a character with a complex backstory, and his going missing in action is a key event that will unfold and reveal more about his past, his relationships, and the overall world of the fanfiction.
One possible plot could be that Natsu discovers his new power as a war god slayer magic user. He then has to face a series of powerful enemies who are threatening the world. Along the way, he might meet new allies who also have unique magic abilities. As he battles these foes, he gradually masters his war god slayer magic and becomes a more powerful wizard.