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.
Maybe in the fanfiction, Erza and Mirajane realize they both love Natsu and instead of fighting over him, they decide to work together. They could start by getting to know Natsu better as friends. As they do this, they discover new sides of Natsu that make them fall even deeper in love. However, Natsu might be more focused on his adventures and his goal of becoming a stronger wizard, which creates a conflict as the girls try to get his attention.
Another idea is that there could be a magical event that causes Erza and Mirajane's feelings for Natsu to be exposed in a very public way. This embarrasses them both, but also makes Natsu aware of their feelings. Natsu, being the kind - hearted but somewhat clueless character he is, has to figure out how to handle this new situation without hurting either of them. He might start to see them in a new light and have to decide if he has any romantic feelings for either of them.
In the fanfiction, their relationships could develop slowly. Erza might start by being more protective of Natsu during battles. She has always been a strong fighter, and now she has an extra incentive to keep Natsu safe. Mirajane, on the other hand, could use her charm and her skills in the guild to make Natsu feel welcome and special. As time goes on, their feelings might become more obvious to other guild members, who could either encourage or tease them about it.
Growth is another theme. Writers like to show how Natsu, Erza and Mirajane develop their magic skills and as individuals over time. For example, Natsu might learn to control his power better, Erza becomes more strategic in battles, and Mirajane discovers new aspects of her magic.
One popular natsu erza mirajane fanfiction is 'The Trio's Adventure'. It focuses on their teamwork and friendship as they go on various quests. The characters are well - portrayed, staying true to their personalities from the original series.
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.
There's also 'Unlikely Allies' which is set during a war against a powerful dark guild. In this story, Natsu, Mirajane, and Erza form an unbreakable alliance, and their individual powers and personalities blend together to defeat the enemy. It has great action scenes and character development.
Their personalities. Natsu is the hot - headed and impulsive one, always ready to jump into action. Erza is the strict and disciplined warrior, bringing order and strategy. Mirajane is the more laid - back but still very powerful one. Together, they create a great balance.
Perhaps the OC is from a different dimension where magic works in a strange way. Natsu, Mirajane, and Erza are intrigued by this. They team up to help the OC understand and control their magic in the world they are in now. Along the way, they encounter a powerful dark wizard who wants to use the OC's unique magic for evil. So, they have to fight together to protect the OC and the world from this threat.
There might be a fanfiction where they participate in a guild - wide competition. Natsu would be all about winning, Erza would be determined to show her strength and uphold her honor, and Mirajane would be there with her own set of skills. In the story, they could form an unexpected alliance with other guild members and through teamwork, overcome challenges and rivals.
The plot might involve Natsu and Mirajane finding a baby dragon in the form of a human baby. Since Natsu has a connection with dragons, he feels a special bond. Mirajane, with her kind heart, steps in to help raise it. They face challenges like protecting the baby from dark guilds who might want to use the baby's power.
One possible plot could be that Naruto somehow ends up in the Fairy Tail world. He meets Erza and Mirajane. Naruto's ninja skills intrigue them. They could team up to fight a common enemy that threatens both the ninja world and the Fairy Tail world. Maybe Naruto teaches them some ninja techniques in return for learning some magic from them.