The sea kings of Mars might be fictional entities. In such stories, they could be powerful rulers of some sort of Martian seas (if we assume Mars had or has seas in a fictional sense). Otherworldly stories could include various elements like strange creatures, different forms of life, and unique landscapes that are not of our Earth.
There could be Martian explorers. They might be the ones who discover the existence of the sea kings of Mars and get involved in the otherworldly events.
I found a few ancient novels. The male and female protagonists are all Sea Kings. The first one was " Your Majesty, Your Character Set Is Broken ". The male lead looked cold and heartless, but he was actually a wife-doting demon. He was gentle and caring, and he knew martial arts. The female lead was a hybrid of an immortal dragon and a demon snake. She had an extreme personality, but she was lively and cute. There would be some misunderstandings and differences between them, but they would eventually be sweet together. In addition," You Sea King, I'm Green Tea " was also a novel. The male and female protagonists were both Sea Kings, and they had a high-level showdown in the story. These novels are all about ancient languages. I hope you will like them.
There's also 'Shirahoshi in the Ninja World'. This one is different as it brings Shirahoshi into the main Naruto world. She has to adapt to the land - based ninja culture, and there are a lot of funny and heart - warming moments as Naruto helps her. It's a very creative take on the two characters.
There is a recommended novel that meets your requirements for the female protagonist of Between Sea Kings, and that is You Sea King, I'm Green Tea. This novel described the complicated relationship between the female lead Ruan Yan and the male lead Shen Jin. The female lead was a green tea girl, while the male lead was the Sea King. This novel might meet your expectations for the female protagonist of the Sea King.
Yes, there are quite a few out there. You can start by looking on popular fanfiction websites like FanFiction.net or Archive of Our Own. Just search for 'luffy and shirahoshi love' and you'll likely find some interesting reads.
You can start by looking on fanfiction.net. It has a large collection of fan - made stories, and there are likely to be quite a few 'Naruto Shirahoshi' ones there. Just use the search bar and type in the relevant keywords.
One common theme is protection. Luffy is often portrayed as Shirahoshi's protector, which then blossoms into love. Another theme could be the contrast between their worlds, with Luffy being a pirate and Shirahoshi a princess of the mermaids.
One common theme is friendship. Luffy is known for making strong bonds, and with Shirahoshi, it's no different. Their friendship is often explored, like how they support each other.
The OC could be a young inventor who comes to Fish - Man Island to study its unique technology. There, they meet Shirahoshi. The OC creates a device that helps Shirahoshi communicate more easily with the surface - dwellers. In return, Shirahoshi shows the OC the hidden secrets of the Fish - Man Island, and they form a strong friendship that transcends the differences between humans and fish - men.