One common theme is the clash of different power systems. Since Nalu comes from Fairy Tail with magic and Naruto has ninja abilities, seeing how they interact and compare is often explored.
Adventure is also a big theme. Nalu is often thrown into the middle of Naruto's world and they embark on adventures together. Whether it's exploring new lands in the Naruto world, or facing off against new threats, the sense of adventure is always there. This includes things like going on missions, exploring ancient ruins, and more that both Fairy Tail and Naruto are known for.
One common theme is the struggle between Natsu's vampiric nature and his love for Lucy. His vampiric instincts might drive him to do things that could potentially harm Lucy, and he has to constantly fight against that. Another theme could be the mystery surrounding his transformation into a vampire. Fans often write about how it happened and what it means for his place in the Fairy Tail guild.
One common theme is the exploration of their relationship in different time periods. For example, seeing how their feelings for each other might have developed differently if they had met earlier or later. Another theme is the idea of changing the past to affect the future. In many nalu time travel fics, they might try to prevent a bad event from happening in the past, which could have a huge impact on their present world.
Another theme might be the unexpected situations that occur due to their drunken state. For example, they could end up in a place they've never been before or get involved in some comical misunderstandings. Also, the 'lemon' aspect might imply a bit of a more mature exploration of their relationship, like a new level of physical closeness or attraction that is explored in a tasteful way in the story.
One common theme could be young love. Since it's set in highschool, Nalu's relationship would be in its budding stage. Another theme might be friendship groups and how they influence Nalu's relationship.
One common theme could be family. Since it involves 'baby Lucy', it might explore how Natsu and Lucy build a family together. Another theme could be adventure in a new way, like how they protect their baby during their adventures.
A very prevalent theme is the idea of 'opposites attract'. Natsu is hot - headed and impulsive while Lucy is more level - headed and organized. Fanfictions play with this dynamic a lot. Also, the theme of sacrifice is common. They are often willing to sacrifice for each other, which shows the depth of their love.
One common theme is adventure. Since Natsu and Lucy are both adventurous characters, their married life in fanfiction often involves going on quests together. Another theme could be domestic bliss, showing them doing normal couple things like cooking dinner together or decorating their home.
One common theme could be the development of an unexpected relationship. For example, in a Nalu teacher - themed fanfiction, there might be the exploration of how Natsu and Lucy, if in a teacher - student type of dynamic (even if not traditional in a sense), grow closer. Another theme could be the over - coming of obstacles. Maybe there are rules against their relationship in the story's setting, and they have to fight against those. Also, self - discovery can be a theme, as they learn more about themselves through their interactions with each other.
Love and friendship are also prevalent themes. Natsu and Lucy's relationship can range from deep friendship to romantic love in different fanfictions. And often, they rely on their friendship with other members of Fairy Tail as well. For example, in many fanfictions, they work together with Gray and Erza to save the guild or face a powerful foe. It's about the power of their combined relationships.
A common theme is the magic of Christmas combined with their love. The Christmas setting can create a more romantic and cozy atmosphere for Nalu. The lemon aspect might bring in some elements of their more private and passionate side. For example, they could have a private Christmas dinner and then some tender moments that are a bit more on the steamy side. There could also be themes related to hope and new beginnings, as Christmas is often seen as a time for that, and their relationship could be evolving in that context.