In fanfiction, Natsu and Mavis could be like a mentor - mentee relationship. Mavis being the first master of Fairy Tail has a lot of knowledge and wisdom. Natsu could look up to her and she could guide him in his journey, much like how Makarov guided him in the main story.
There could also be a scenario where Natsu is seen as a sort of protector of Mavis's legacy. Since Mavis founded Fairy Tail, Natsu, who is one of the most powerful members, might feel a strong sense of duty to uphold what she started. He could go on quests specifically related to protecting the history and values that Mavis instilled in the guild.
Well, in many fanfictions, their relationship might start with Natsu being a bit in awe of Mavis as she is a very important figure in Fairy Tail's history. Natsu, being his brash self, might initially make mistakes around her but gradually learns from her wisdom. As time goes on, he could come to respect her even more deeply and they might form a bond where Mavis becomes like a guiding light for Natsu in his adventures and growth within the Fairy Tail guild.
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.
In fanfiction, Mirajane and Natsu could have a very interesting mentor - mentee relationship. Mirajane, being more experienced, could teach Natsu some new magic techniques or how to better control his power. This would add a new dynamic to their interactions within the Fairy Tail guild.
In fanfiction, the relationship between Mavis and Zeref can be complex. Some fanfictions might explore their connection in a more romantic light, delving into how their different natures, one being the powerful wizard and the other with his own dark powers, interact. It could be a story of star - crossed lovers, with their fates intertwined due to the overarching plot of Fairy Tail.
One unique plot point could be Natsu having to learn magic in a completely different way under Mavis' tutelage. Instead of his usual hands - on, instinctive approach, he has to study theory and history. Another could be Mavis using Natsu to revive some long - lost traditions of the Fairy Tail guild. Maybe Natsu discovers a hidden power within himself that was dormant until Mavis guided him.
In a fight between Natsu and Mavis in a fanfiction, it's really hard to say who would win. Natsu is extremely powerful with his dragon slayer magic, being able to take on some really tough foes. However, Mavis is the first master of Fairy Tail and has a great deal of wisdom and powerful magic herself. It could really go either way depending on how the fanfiction writer wants to portray the battle.
In some fanfictions, Natsu's dragon slayer magic and Mavis's Fairy Law could be combined in a unique way. For example, Natsu could use his fire to enhance the power of Mavis's Fairy Law, making it more destructive against their enemies.
Another way their relationship could develop is through a common goal that is not directly related to fighting. For instance, they both want to revive an old Fairy Tail tradition that has been forgotten. They work together to research, gather materials, and convince other guild members. During this process, they bond over their shared love for the guild and for the things that make Fairy Tail special, which in turn deepens their relationship.
Some fanfictions depict their relationship evolving as they participate in guild - wide events. For instance, during a festival or a celebration in the guild, they might have a conversation that reveals new aspects of their personalities to each other. Over time, these small interactions build up, and they become closer friends, or in some cases, the relationship might take on a more romantic undertone as the fanfiction writer chooses to explore that aspect.
In fanfiction, the relationship between Natsu and Erza's child and the other Fairy Tail members would be quite diverse. The child would be part of the Fairy Tail family. Wendy would be like an older sister, helping the child with their magic and always being kind. Cana might teach the child some of her card tricks and gambling skills in a more innocent way. Elfman would be the one to encourage the child to be manly, and Evergreen would be that strict but caring mentor figure. They'd all contribute to the child's growth and development within the guild.