The girl OC could have been a street performer before joining Fairy Tail. Her guitar was her only means of survival. One day, she witnessed a Fairy Tail mage doing a great deed. Inspired, she decided to seek out Fairy Tail. The guitar has seen her through tough times on the streets, and now in Fairy Tail, it becomes a symbol of her journey from being alone to being part of a big family. She uses the music from her guitar to tell her story to the other members of the guild.
A fanfiction might focus on a love story between Leo and Aries. They could meet in the celestial spirit world during a time of upheaval. Leo, being the brave lion, protects Aries from the chaos. As they spend more time together, they realize their feelings for each other and have to navigate the challenges of being celestial spirits in love, like dealing with the rules of the spirit world and their contracts with their mages.
One great Aries and Leo fanfiction is 'The Celestial Bond'. It beautifully explores their relationship within the Fairy Tail universe. The author does an amazing job of bringing out their personalities. Aries' shyness and Leo's bravado play off each other really well in this story.
One common theme is Leo's relationship with the other guild members. It often explores his loyalty and how he interacts with them in different situations.
Maybe a fanfiction where Leo and Aries are the only two celestial spirits left after a great war in the spirit world. They have to find a way to repopulate the spirit world. They travel to different realms in search of a solution, facing many dangers along the way. Along their journey, they learn more about each other's strengths and weaknesses and develop a deep bond that is more than just friendship.
In some fanfictions, Erza's father could be a powerful mage who was lost in a great battle against dark forces. His absence then becomes a driving force for Erza's growth and her determination to fight evil.
One common theme is redemption. Given Leo's complex backstory in 'Fairy Tail', many fanfictions explore his journey towards redemption. For example, he might be trying to make up for past mistakes.
In a fanfic, their relationship could develop romantically. They might start by sharing small moments together, like watching the sunset after a mission. As they continue to interact, they find that they have a lot in common despite their differences. Aries' gentle nature softens Leo's more brash side, and Leo's passion makes Aries feel more alive. Their relationship could be a slow - burn one, with lots of tender moments and a few obstacles along the way, such as other characters being jealous or disapproving, but in the end, they could end up together.
A great fanfiction idea could be that Lucy and Leo get transported to an alternate dimension. In this dimension, the rules of magic are different, and they have to figure out how to get back home while also dealing with the strange new magical creatures and challenges there. This would test their relationship and their individual skills.
I'm not sure who the absolute best is, but some popular authors might be those who have a deep understanding of the Fairy Tail universe. They would be able to write Leo and Ar in a way that stays true to their characters. For example, an author who has been a long - time fan of Fairy Tail and has studied the lore and character traits.