A possible plot could be that Romeo gets poisoned by a dark magic user. Wendy, with her healing magic, tries to save him but in the process, she has to enter Romeo's subconscious. Inside, they relive some of their shared memories and also face some of their hidden fears. This journey in his mind brings them closer and when Wendy finally heals Romeo, their relationship has a new level of understanding and closeness.
One idea could be that Wendy and Romeo get caught in a magical storm that transports them to a parallel world where their powers are reversed. They have to learn to adapt and rely on each other in new ways to find their way back home.
Maybe they accidentally get transported to a parallel world where the roles in Fairy Tail are all reversed. There, Wendy has to be the brave one leading Romeo through all the chaos to find a way back home. This could lead to a lot of character development and interesting interactions between them.
One idea could be that Romeo and Wendy discover a hidden magic in the Fairy Tail guild that only they can control together. This magic could be related to an ancient prophecy.
One idea could be Romeo and Wendy going on a secret mission together to save a small village from a dark magic spell. They discover that they have to combine their magic in a new and unique way to break the spell.
They could start off as friends helping each other with their respective magic training. As they spend more time together, they notice little things about each other that they find endearing. For example, Romeo might notice how Wendy is always so gentle when she heals the guild's small pets, and Wendy might notice Romeo's determination when he takes on difficult quests.
The fanfic could center around Wendy and Romeo's relationship development. For example, they start as friends but as they go through various challenges, they realize their feelings for each other are deeper. It could also involve other Fairy Tail members helping or hindering their relationship growth.
One idea could be Romeo going on a solo adventure to discover a hidden magic in Fairy Tail's history. He stumbles upon an ancient spellbook that gives him new powers, but also attracts the attention of dark wizards who want it for themselves.
Perhaps a plot where Romeo gets into trouble with a dark magic user and Chelia has to rescue him. This could involve Chelia using her unique wind magic in creative ways to defeat the villain. They could also have some deep conversations during the rescue mission about their feelings for each other and their place in the Fairy Tail guild.
One idea could be Romeo going on a magical adventure with his harem members to save the Fairy Tail guild from a new dark threat. They might use their combined magical abilities to overcome obstacles.
A possible plot idea is that Romeo discovers Juliet has a special and rare magic ability that his guild wants to control. He has to choose between his loyalty to the guild and his love for Juliet. Meanwhile, Juliet is also conflicted as she doesn't want to be used for her power but also doesn't want to lose Romeo. This creates a complex web of emotions and decisions, much like the original Romeo and Juliet story.
One idea could be that Doranbolt discovers Wendy has a hidden power that is linked to his own past. Maybe they have to team up to fight an ancient evil that only their combined powers can defeat.