First, understand the characters well. Luffy is carefree and driven by his dreams, while Smoker is strict and upholds justice. For the 'lemon' part, if you want to add a romantic or more adult - themed element, do it in a way that is in - character. Maybe start with building a unique plot where they are forced to interact in a new way, like being stranded on an island together.
One example could be a story where Luffy and Smoker are forced to team up during a strange pirate - marine alliance situation. In this fanfiction, their initial animosity slowly turns into mutual respect as they face a powerful common enemy. The 'lemon' aspect might be subtly added with some underlying romantic tension that builds between them during their adventure.
Another theme is friendship development. Since they start as adversaries, many fanfictions show how they slowly become friends or at least respect each other more. For example, they might find common ground in protecting the innocent or in taking on a powerful villain.
One popular luffy x smoker fanfiction is 'The Unlikely Alliance'. It delves into a scenario where Luffy and Smoker are forced to work together against a common enemy. Their contrasting personalities create interesting dynamics as they navigate through challenges.
There's 'Smoker's Dilemma'. In this fanfic, Smoker is constantly conflicted between his duty as a marine and his growing understanding of Luffy's ideals. It's really interesting to see how their relationship develops over the course of the story.
A great Smoker x Luffy fanfic stands out when it explores their ideological differences. Luffy is all about freedom and adventure, while Smoker is a marine with a sense of justice. When a fanfic delves into how they can coexist or even learn from each other, it becomes really engaging.
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.
A possible plot is that Fem Luffy accidentally gets involved in one of Smoker's investigations in a new island. She initially seems like a hindrance to him, but as the story progresses, they find out that there is a much larger conspiracy at play that involves both the Marines and some powerful pirate groups. They have to work together to expose the truth, and during this time, a strange friendship starts to form between them.
Their relationship could start as one of mutual distrust. Smoker sees Fem Luffy as a pirate and Fem Luffy sees Smoker as a Marine who might try to arrest her. But as they face common enemies and challenges, they gradually start to respect each other. For example, if they are both trying to stop a mad scientist from creating dangerous weapons on an island. Through this shared goal, they see each other's strengths and the relationship moves from distrust to a sort of grudging respect.
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.