One common theme is love. Since Boa Hancock has a crush on Luffy, many fanfics explore how this love could develop. Another theme is adventure. Luffy is always on an adventure, and fanfics often involve Boa joining him in his escapades.
The theme of self - discovery can also be present. Hancock might discover new sides of herself because of her relationship with Luffy. For example, she could become more open - minded or learn to trust others more, which is a big step for her as the empress of Amazon Lily.
A big theme is also about breaking barriers. Hancock is a proud and strong woman from Amazon Lily, and Luffy is a carefree pirate. Their relationship in fanfics often shows how they break cultural and social barriers between them. For example, Hancock's tribe has certain traditions and views about men, but with Luffy, she defies some of those. Also, friendship is a theme as Luffy values friendship highly and Hancock becomes part of his circle of friends in a special way.
One popular type of 'luffy boa hancock fanfiction' often involves their adventures together on the high seas. Writers might create scenarios where Hancock uses her powers to protect Luffy during a difficult battle. Another common plot is about how their relationship develops over time, starting from Hancock's initial infatuation with Luffy and how Luffy, in his own unique way, comes to understand and care for Hancock.
One popular 'Boa Hancock x Luffy' fanfic is 'The Pirate's Heart'. It explores their relationship in an interesting way, with great character development for both. Another one could be 'Love on the Grand Line' which has some really sweet moments between them.
I'm not sure specifically which 'luffy x boa lemon fanfic' is the best. But you can try searching on some popular fanfic websites like FanFiction.net or Archive of Our Own. Maybe look for ones with high ratings and positive reviews.
Often, the theme of adventure might be intertwined. Given that Luffy is all about exploring and Boa has her own story in the One Piece world. Their relationship could be set against the backdrop of new adventures they embark on together. Another theme could be the discovery of emotions. Luffy is not always in touch with his romantic feelings, and Boa has her own complex emotions, so fanfics may focus on how they come to terms with their feelings for each other.
One popular 'boa and luffy fanfic' is 'The Pirate's Heart'. It focuses on their unique relationship and the adventures they could have together. Another one might be 'Boa's Obsession' which delves into how Boa Hancock's feelings for Luffy could develop in different scenarios.
In the One Piece world, Luffy is on this grand adventure and Hancock is a powerful figure. Their relationship has this allure of the unexpected. Fans are drawn to the idea of these two very different characters coming together. Fanfic writers can play with their personalities and create all sorts of interesting scenarios. For example, Hancock's initial haughty attitude towards most people but her special soft spot for Luffy makes for great storytelling. It's also about the idea of love in a world full of pirates and battles, which is quite appealing.
Another one is 'Luffy and Hancock: A New Chapter'. This fanfic could start with a new arc where Hancock decides to join Luffy's crew for a short time. It explores how the crew members react to her presence, and how Luffy and Hancock's relationship grows during this time, with some comical and heart - warming moments.