Nami could be a main character. She would be very worried about Luffy and try to find him. She might use her navigation skills to track down Law's ship. And she could be the one to try and negotiate with Law for Luffy's release.
First, you should definitely check out AO3. It has a well - organized tagging system, so if you search for 'ace protects luffy', it will show you relevant fanfictions. FanFiction.net is also a good bet. Some of the fanfictions on there might be a bit older but still very good. Additionally, you could join some One Piece - themed Discord servers. People often share and discuss fanfictions in those communities, and you might come across some 'ace protects luffy' ones.
One popular 'ace protects luffy fanfiction' story could be 'Ace's Unwavering Shield'. In this, Ace is always there to fend off any threats towards Luffy. He uses his devil fruit powers in creative ways to keep Luffy safe during battles. Another is 'Protecting the Dreamer', where Ace not only protects Luffy physically but also defends his brother's dreams against those who try to crush them.
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.
In many Luffy fanfictions, a jealous Law can be quite an interesting character. He might be jealous of Luffy's popularity among the crew or his carefree attitude. This jealousy could lead to some tense moments between them, like when Law tries to outdo Luffy in certain tasks just to prove himself better.
I really like 'Luffy and Law's Shared Destiny'. It shows how their fates could be intertwined in a more romantic way. The story has some really sweet moments between them, like when they share their dreams under the starlit sky during a break in their journey. It also adds new elements to the One Piece world they exist in.
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 adventure. Since they are both from the One Piece world which is full of high - seas adventures. Another theme could be friendship development. As they get to know each other better, their relationship evolves. Also, there might be themes of mutual respect as they recognize each other's strengths.