Well, a great plot could be that the OC is a former enemy who has a change of heart. He was once part of a dark guild but realizes the error of his ways. Lucy is the first to see the potential for good in him. They start training together, and the OC discovers he has a special connection to Lucy's celestial spirits. Maybe he can communicate with them in a way that Lucy can't. This leads to them uncovering a mystery about the origin of celestial spirits. Another option is that the OC has the power to create portals to different dimensions. He accidentally pulls Lucy into a dangerous dimension. They have to rely on each other to find their way back, and in the process, their relationship blossoms.
An interesting plot might be that the OC is a long - lost relative of Lucy. They meet at Fairy Tail and initially don't realize their connection. The OC has a strange and powerful magic that attracts Lucy's attention. As they work on various missions together, they start to notice similarities between them. Eventually, they discover their relation, but by that time, they have already fallen in love. Another plot could be that the OC is an artist who can bring his drawings to life. He draws a picture of a new celestial spirit, and Lucy's keys start to react to it. They embark on a journey to find out if the spirit is real and how it relates to her magic. Along the way, their feelings for each other grow.
One plot idea could be that Flare and Lucy are forced to team up on a mission. They start off not getting along due to their past differences. But as they face challenges together, like fighting a powerful dark mage, they begin to understand each other. Flare might learn about Lucy's kindness and determination, and Lucy could see Flare's hidden insecurities. Eventually, they form a strong friendship that could potentially turn into something more.
One idea could be that Mira and Lucy team up for a really difficult S - Class quest. They face all kinds of magical creatures and obstacles along the way. Mira uses her demon form's powers in a creative way to protect Lucy, and Lucy discovers a new Celestial Spirit that helps them out.
Another plot idea is that Lucy, while on a mission, discovers a strange magical artifact that has a connection to Naruto's world. She accidentally activates it and it summons Naruto. Together, they have to figure out how to send Naruto back while also dealing with the chaos that the artifact's appearance has caused in the Fairy Tail guild. For example, it could be causing some of the guild members to have strange powers or behaviors similar to those in Naruto's world.
Maybe an OC who has the ability to communicate with spirits. In the 'fairy tail x oc fanfiction', this OC could discover that there are ancient and powerful spirits that are about to be awakened due to some dark magic ritual. The OC tries to enlist the help of the Fairy Tail guild to stop this from happening. Along the way, they face many challenges and also have to deal with the guild's initial skepticism about their powers and the existence of these spirits.
One idea could be that Naruto and Lucy end up in a parallel dimension where they have to team up to defeat a common enemy. Naruto's powerful jutsu combined with Lucy's celestial spirit magic would make for some epic battle scenes.
One idea could be a story where Hughes and Lucy are on a mission together in a mysterious, uncharted land. They have to rely on each other's skills to survive. Hughes' strategic mind and Lucy's celestial spirit magic combine in unique ways to overcome the obstacles they face, like dangerous magical beasts and complex mazes.
One idea could be that the OC has a special power that Mavis senses and they form a connection through it. For example, if the OC can communicate with ancient spirits and Mavis, being an ancient and powerful mage, is intrigued by this ability. They could then embark on a journey to discover more about the origin of this power and in the process, develop a deep friendship or more.
The OC could be a time - traveler who ends up in the Fairy Tail world. She meets Natsu and tries to hide her true identity. But Natsu, being perceptive, notices something odd. They start to team up for various missions, and the OC has to use her knowledge of future events to help Natsu and Fairy Tail, all the while falling for Natsu's brash but kind personality.
A plot could involve Freed accidentally casting a spell that links his and Lucy's minds. At first, it's a chaotic mess as they have to deal with suddenly sharing thoughts and feelings. But as time goes on, they start to understand each other on a deeper level. They use this newfound connection to uncover a plot within the Fairy Tail guild by a group of mages who are trying to undermine the guild's leadership, and in the process, their relationship blossoms.
One plot idea could be that Lucy discovers a cat with magical powers that is related to an ancient Fairy Tail legend. The cat could lead her on a quest to find a hidden treasure that was lost long ago in the world of Fairy Tail.