I don't recommend exploring lemon fanfictions as they often involve inappropriate content. But generally, if they exist, they might have themes of possessiveness in the relationship.
Since this involves a rather inappropriate type of fanfiction, it's hard to say positive common themes. However, some might wrongly distort the relationship into something overly sexualized with themes like physical attraction being overemphasized, which is not in line with the nature of the characters in the original work.
One common theme is the exploration of their different outlooks on life. Luffy is all about freedom and adventure, while Law has his own set of goals and a more complex backstory. Another theme could be the power dynamics between them, as they both have strong abilities in the One Piece world.
One common theme could be the exploration of their different personalities. Luffy's carefree and Law's more reserved nature can create interesting dynamics. Another theme might be their shared adventures in the One Piece world, and how their relationship develops during those times.
A common theme is the exploration of their friendship. Given their alliance in the original story, fanfictions often expand on how they become closer and trust each other more. For example, they might face a powerful enemy together and through that experience, their bond deepens.
One common theme is the exploration of their contrasting personalities. Luffy is so carefree and Law is more reserved. Fanfictions often play with how they interact and influence each other because of these differences. For example, Luffy might make Law loosen up a bit and Law might make Luffy think more strategically at times.
One common theme is the exploration of their different personalities. Luffy is carefree and Law is more serious, and how they balance each other out as soulmates. Another theme is adventure. Since they are pirates, their soulmate journey often involves going on quests and facing challenges together. Also, the theme of discovery is there. Discovering the depth of their soulmate bond as they interact more.
Another theme is the idea of trust and loyalty. In many fanfictions, they start off as distrustful of each other but gradually develop a deep sense of loyalty as they face challenges together. For example, in some stories, they have to rely on each other to survive in a dangerous situation, which cements their relationship. It shows how two very different characters can form a strong bond.
Luffy x Law fanfiction often explores unique relationships. In such works, the interactions between their distinct personalities can be really interesting. Luffy's carefree and bold nature contrasts with Law's more reserved and strategic side. The 'lemon' aspect might add some romantic or tense elements to their relationship, but it also depends on how the author portrays it.
One common theme is friendship. Fans like to explore how their different personalities can form a strong bond. Luffy's carefree and positive nature contrasts with Law's more serious and calculated demeanor, and seeing how they interact as friends is a popular theme.
One common theme is friendship. Despite their differences, fanfiction often shows them becoming close friends. Another theme is adventure. They might embark on new and dangerous quests together. And power - up themes are also there. Maybe they learn new abilities from each other or find ways to combine their powers for a greater good.
Another theme is self - discovery. The female Luffy in these fics often discovers new aspects of herself through her interactions with Law. And Law, in turn, might also learn more about his own feelings and capabilities while being with her. This mutual growth is a common thread in many 'law x fem luffy fanfic'.