The plot could involve 'her' having a special power that is needed by Fairy Tail. Natsu realizes this and wants her to join. However, 'her' has some secrets or a past that she's afraid will be exposed if she joins. Natsu helps her overcome her fears, and as she joins Fairy Tail, they all face a new big threat together, where her power becomes crucial in saving the guild.
Perhaps there's an antagonist who doesn't want 'her' to join Fairy Tail. This creates a conflict. Natsu has to fight against this antagonist to protect 'her' and ensure she can join the guild. Along the way, 'her' might start to develop feelings for Natsu as she sees how much he cares about her joining.
Well, without more context, 'her' could be any number of characters. It might be a new character created for the fanfiction. Natsu might want her to join Fairy Tail because he sees potential in her magic abilities. Fairy Tail is all about accepting people with different powers and making them part of the family.
If Natsu and Zeref join Fairy Tail in fanfiction, it would change the dynamic of the guild completely. The other members would have mixed reactions. Some might be distrustful of Zeref due to his past actions. However, as time passes, they could see the good in him. Natsu and Zeref together could attract a lot of attention from outside forces. Enemies might target Fairy Tail more because of their combined power. But also, they could inspire the guild to become even stronger, with everyone striving to keep up with their new powerful comrades.
It could be about Natsu having left Fairy Tail for some reason and then reuniting with the guild in a very unexpected way. Maybe he has new powers or a different outlook on life that causes some friction and also some amazing moments of reunion and growth within the guild.
Well, one possibility is that Natsu could join Fairy Tail in a different way than in the original story. Maybe he has some special mission before officially becoming a member. For example, he has to prove his loyalty by helping an elder member with a personal problem.
One possibility could be that Natsu is attacked due to a misunderstanding within the Fairy Tail guild. Maybe a new member misinterprets Natsu's actions as a threat and attacks him in self - defense.
In this fanfiction, the story might take a darker turn. Natsu is like the heart and soul of Fairy Tail in many ways. Without him, there could be a sense of gloom in the guild. However, this could also be a catalyst for change. Characters like Wendy could step up more. She might start to explore and master her dragon slayer magic in ways she hadn't before. And the relationships between the characters would shift, perhaps becoming more complex as they deal with the absence of Natsu.
One possible plot could be that there is some sort of misunderstanding or dark magic at play that causes Natsu and Mavis to fight. Natsu, being hot - headed, jumps into the fray without fully understanding the situation. Mavis, on the other hand, is trying to figure out a way to stop the fight without harming Natsu. As the battle progresses, they both start to realize that they are being manipulated and then team up to face the real enemy.
One possible plot could be that the guild goes into deep mourning. Gray might blame himself, thinking he could have protected Natsu. Lucy could be in a state of shock and disbelief, and she might start writing in her diary about all their adventures, as if reliving the memories to deal with the pain.
One possible plot could be that Natsu has been living a different life away from Fairy Tail. Maybe he was raised by another guild unknowingly. When he finally joins Fairy Tail later, he has to prove himself to the existing members who are skeptical of his late arrival. He might have unique magic skills he developed elsewhere that surprise everyone.
The story could start with Natsu being tricked by a powerful enemy and sent to a far - off and unknown land. As a lost Fairy Tail member, he would have to rely on his instincts and the little magic he has left. He might meet new allies who help him in his journey back to Fairy Tail, all while learning important lessons about friendship and the true strength of his guild.