A possible storyline is a friendly competition between them. They bet on who can complete a series of challenges first. These challenges could involve things like rescuing a certain number of people in a village within a time limit, or collecting rare magical items. Along the way, they learn more about each other's strengths and weaknesses, and also grow closer as friends. This kind of storyline can also have some humorous moments, like when Natsu accidentally sets something on fire during a task that Gray then has to quickly freeze to prevent a disaster.
Another storyline could involve the reactions of their friends in Fairy Tail. Some might be overjoyed and helpful, like Levy who could give Lucy advice on pregnancy. Others, like Gray, might tease Natsu about becoming a father. Their friends could also organize a big celebration for the upcoming baby, which would show the strong sense of community in Fairy Tail.
Another common plot is Gray getting jealous when Lucy is getting too much attention from other guys in the guild. This jealousy leads to some really interesting interactions between them, like Gray trying to show off in front of Lucy in a really cute and clumsy way.
There are also storylines that focus on their friendship growth. Maybe they start off not getting along well because of their different personalities. Gray is more stoic and Lucy is more outgoing. But then through various adventures together, they come to understand and respect each other, and this forms a deep bond of friendship that is central to the fanfiction.
A common storyline is when Lucy's celestial spirits play a role in bringing Lucy and Natsu closer. For example, one of her spirits could give Natsu a task that involves protecting Lucy at all costs. This leads to them spending more time together and sharing deeper conversations. Another idea is that a powerful enemy targets Lucy specifically because of her connection to the celestial world, and Natsu is determined to keep her safe no matter what. This shows his loyalty and could develop into a more romantic relationship as the story progresses.
One great storyline could be that Natsu discovers he has a long - lost relative who is in danger, and Lucy helps him find and protect this family member. It could involve a journey to a mysterious place filled with magical creatures that they have to face together.
One idea could be a story where Lucy discovers a powerful magic that can only be controlled with the combined help of Natsu and Gray. So, they have to put aside their usual rivalries and work together closely. This could lead to some really fun and intense training sessions between them as they try to master this new magic.
Some fanfictions focus on a time - travel storyline. Natsu and Lucy might be sent back in time to an important era in Fairy Tail's history. There, they have to ensure that certain events happen correctly to safeguard the future of the guild. Along the way, they interact with past versions of the guild members and experience things that change their perspective on their own relationship and the guild as a whole.
Their relationships can be developed through shared experiences. For instance, if they go on a dangerous quest together, they'll have to trust and rely on each other. This can deepen their friendship. Natsu might start to respect Gray's ice - magic more when he sees how it can complement his own fire - magic in battle. Lucy could become closer to both of them as she uses her celestial spirits to assist them in tight situations.
One great Gray and Lucy fanfiction is 'A New Bond'. It focuses on their adventure together in a mysterious land, where they have to rely on each other's skills. Gray's ice - making magic and Lucy's celestial spirits work in harmony to overcome challenges.
A fanfiction could show their friendship developing through their shared love for Fairy Tail. They all have different reasons for loving the guild. Lucy loves the sense of family, Natsu loves the adventure, and Gray loves the chance to better himself. They start to realize that they have more in common than they thought. They begin to train together, help each other with personal problems, and before long, they have a strong, unbreakable friendship within the walls of Fairy Tail.