Well, without reading the specific 'natsu and hisui' fanfiction, it's hard to say in detail. But generally, it might be about their relationship, perhaps an adventure they go on together, or how their personalities interact. It could be a story that explores their characters in a new and unique way.
Yes, there might be some out there. You can start by checking fanfiction platforms like FanFiction.net or Archive of Our Own. Just search for 'natsu and hisui secretly married' and you'll likely find several stories. However, the quality can vary greatly, so you may need to read a few to find one that suits your taste.
People like 'natsu and hisui love fanfiction' because it combines two interesting characters. Natsu is a well - loved character with his energetic and brave nature, and Hisui is also an appealing character. Their relationship in fanfiction offers a new perspective on the existing fictional world.
There's also 'Love Beyond Guilds'. It shows how Natsu and Hisui's relationship develops despite being from different guild - related backgrounds. Natsu is from Fairy Tail and Hisui has her own set of responsibilities. But their love manages to bridge those gaps. It's a story full of adventure as they go on quests together and face various challenges that test their relationship.
It could be that Natsu underestimates the strength of the final boss guarding Princess Hisui. During the intense battle, he takes several hard hits but refuses to give up. He endures the pain and uses his last bit of strength to defeat the enemy and save the princess.
They might have a very unique wedding. Since Natsu is from a world full of magic, there could be magical elements everywhere. Maybe the flowers are enchanted to sing during the ceremony. Hisui, coming from a noble family, would want it to be a grand affair. There could be a large gathering of people from different regions. Natsu's friends from his guild would be there, adding a touch of rowdiness and fun to the otherwise formal event.
One common theme is sacrifice. Natsu is willing to put himself in harm's way for the princess, which shows his selfless nature. Another theme could be loyalty, as he is loyal to the princess and to the idea of protecting the innocent. Also, there might be a theme of recovery, as Natsu has to recover from his injuries, which can show his strength and the support he gets from his friends and the princess herself.
Typically, it might start with them falling in love secretly. Maybe they meet in some secluded place often and develop feelings over time. Then, they decide to get married in a private ceremony, perhaps with only a few trusted friends or family members (if any) present. After that, they would have to deal with the challenges of keeping their marriage a secret, like hiding it from their respective friends or groups they belong to.
He might get seriously injured. For example, he could be poisoned by some magical creature protecting the princess. This would make him weak and in pain but still push through to save her.
Well, a great storyline might involve Hisui getting lost in a dangerous magical realm and Natsu being the one to go and rescue her. During their time in the realm, they rely on each other's strengths. Hisui uses her knowledge and diplomatic skills, while Natsu uses his brute strength and dragon slayer magic. This shared experience brings them closer. Or perhaps there's a prophecy about Hisui and Natsu that they initially don't believe in, but as events unfold, they start to see the truth in it.