One possible plot could be that Lucy and Juvia leave Fairy Tail to go on a self - discovery journey. They might want to explore their individual magic powers more deeply without the constraints of the guild. Maybe they travel to different magical realms, meet new characters, and learn unique magic techniques that they can bring back to Fairy Tail later.
A powerful magical being from another dimension could be the main antagonist. This being senses the departure of Lucy and Juvia from Fairy Tail and sees it as an opportunity to invade their world. It tries to stop the two girls from getting help or finding a way to stop it, as they are two of the most powerful mages outside of the guild protection now.
A possible reason could be personal conflicts within the guild. Lucy might have an issue with some of the guild's rules or how certain things are run. Juvia could be following Lucy for some reason, like loyalty or because she also has her own issues with the guild. For instance, if there are tensions between Juvia and other members over Gray.
One possibility is that the guild would experience a significant emotional impact. Lucy is a central figure, and her celestial spirit magic has been crucial in many battles. Juvia, with her water magic, is also a strong member. Their departure might lead to a decrease in the guild's overall power. Some members might feel betrayed, while others could be motivated to find out why they left and try to bring them back.
In some fanfictions, Juvia and Lucy could be in a situation where they have to rescue a kidnapped guild member. Juvia uses her water magic to track the kidnapper's location through the moisture in the air. Lucy uses her keys to call upon spirits that can help in combat and stealth. Along the way, they face many challenges and have heart - to - heart conversations. This experience deepens their friendship and they become closer allies within the Fairy Tail guild.
One interesting Juvia Leaves Fairy Tail fanfiction could be one where she goes on a solo adventure to discover her true powers outside of the guild. In this type of fanfic, she might encounter new magical creatures and have to rely solely on her own skills.
A possible fanfiction could be that Juvia leaves to protect the guild. She discovers a dangerous plot against Fairy Tail and decides that her absence would be the best way to keep everyone safe. As she is away, she secretly works to thwart the evil plan, and in the end, she returns victorious, having saved the guild she loves so much.
A fanfiction could also explore a scenario where Lucy and Juvia enter a magic tournament together as a team. They face various opponents and use their combined skills to win. Their opponents might underestimate them at first because they seem like an unlikely pair. But they prove everyone wrong with their strategic use of magic. Lucy could summon spirits to distract opponents while Juvia attacks with powerful water spells.
Often, in fanfiction, a common plot is that Juvia and Lucy are paired up for a task. This forced proximity makes them learn about each other. Lucy might introduce Juvia to new ways of using magic in a more creative way, while Juvia shows Lucy how to be more in tune with her emotions. As they face difficulties together during the task, they build a bond of trust. This trust then evolves into a deep friendship where they are always there for each other, whether it's cheering each other on during a magic competition or comforting each other after a loss.
It could be that Lucy leaves Fairy Tail because of a personal quest she has to undertake. This quest might be related to her family or her past, and she feels that she has to do it alone without the support or interference of the guild. She may plan to return once she has completed this important task.