One possible plot could be that they discover the pregnancy and then face challenges together. Maybe they have to deal with the reactions of their friends in the guild, some being happy and supportive while others might be worried about how it will affect their adventuring lives.
Another aspect could be that the pregnancy reveals some secrets or powers. For example, the unborn child might have some unique magical abilities that start to show even before birth, and Erza and Natsu have to figure out how to handle this while also keeping the baby safe from any potential threats in their magical world.
Perhaps in the fanfiction, Natsu meets Erza in a completely new setting, like a parallel universe where the Fairy Tail guild doesn't exist yet. They start off as strangers but quickly realize they have similar goals. Erza might initially be a bit distrustful of Natsu's wild ways, but as they face challenges together, such as a group of bandits attacking a village, they learn to trust and rely on each other.
One possible plot is that a time - travel or alternate - reality situation occurs where Natsu and Erza are already married and have a baby. The story could show how they adjust to this new family life. Natsu might be the fun - loving dad who plays with the baby using his fire powers in a safe way, while Erza is the strict but loving mom who makes sure the baby is well - behaved and learns proper values. They would also have to deal with the reactions of their friends in the guild, some of whom might be shocked or overly excited about the new addition to their family.
Well, perhaps Erza was tricked into believing something false about Natsu. Maybe she was misled by some enemy who made it seem like Natsu was going to endanger the guild. So, in her sense of duty to protect the guild, she took actions that Natsu perceived as betrayal.
It could be about a misunderstanding. Maybe Natsu is under a lot of stress or has been wrongly accused, and Erza's actions or words accidentally trigger his outburst.
One idea could be exploring how their guild mates react to the news. Some might be overjoyed and offer all kinds of support, while others could be a bit shocked at first. Another could be focusing on how Natsu and Erza themselves adjust to the idea of becoming parents. Natsu might be a bit clumsy at first but full of enthusiasm, and Erza could be more practical and start planning everything right away.
One plot could be that Natsu becomes overly protective of Erza. He starts to take on extra jobs to save up for the baby. Meanwhile, the guild members also rally around them. Gray might tease Natsu about being a soon - to - be - dad, and Lucy could offer to help Erza with baby - related preparations like knitting baby clothes.
One possible plot could be that Natsu and Erza are sent back in time to a crucial moment in the history of their guild. Maybe they go back to the time when the guild was first founded. They could end up having to protect the founders from a threat that was long forgotten in their own time. This would give them a chance to see how the guild started and also change some things for the better in the present.
Well, it could be about a powerful encounter. Maybe Erza initially mistakes End Natsu for the regular Natsu and there's some confusion. Then they might have a fight as Erza is always ready to combat threats. But as they engage, they could discover things about each other that change their views.
One possible plot could be that Natsu starts having dreams about Erza. These dreams make him realize his feelings for her. He then tries to get closer to her by going on more missions together. Along the way, he discovers little things about Erza that he adores, like her love for strawberry cake.
Well, one possible plot could be a love triangle situation. Erza and Mirajane both have feelings for Natsu, but Natsu is oblivious to their affections. They might compete in a friendly way at first, like trying to be the one to give Natsu the best meal or help him with his training. This could lead to some humorous moments as Natsu just doesn't pick up on their real intentions.