The theme of growth in their relationship is also prevalent. As they come to terms with being soulmates, they grow both individually and as a couple. They learn to understand each other better, communicate more effectively, and support one another through difficult times, which is really beautiful to see in these fanfictions.
One great marco x ace soulmate fanfiction is 'The Bond of Souls'. It beautifully depicts their journey of realizing they are soulmates. The author does an amazing job of showing their emotional connection through various adventures they share.
One common theme is friendship. Ace, the reader, and Marco often form a strong bond of friendship that can withstand various challenges. Another theme is adventure. They might go on quests or face dangerous situations together. Love, in a platonic or sometimes romantic sense, is also a theme. The characters care deeply for each other and support one another through thick and thin.
Friendship is a very common theme. Given their relationships in the original story (assuming it's One Piece - related), fanfictions often explore the deep bond between Marco, Ace, and Thatch. They might show how they support each other through various challenges.
Growth is a prevalent theme. As they go through various battles and experiences in the fanfictions, they grow both as individuals and in their relationship. Their understanding of each other and their own abilities develops. Additionally, the theme of brotherhood is strong. They are like brothers in the crew, and this brotherly love is often a central focus in these fanfictions.
One great 'ace x reader x marco fanfiction' is 'A Triad of Hearts'. It beautifully portrays the relationship between Ace, the reader, and Marco. The story has some really touching moments where the characters interact in unique ways. Another one could be 'Among the Flames and Wings' which focuses on the adventures the three might have together. It has a good plot that keeps you engaged throughout.
One popular place to find marco x ace x thatch fanfiction is Archive of Our Own (AO3). Just go there and search for the relevant tags. You'll likely come across a variety of stories with different themes and plotlines.
One of the key themes could be loyalty. In a possessive relationship in this fanfiction, Ace and Marco might show extreme loyalty to each other. They could be possessive because they don't want to lose what they have in each other. Another theme might be sacrifice. Given their personalities in One Piece, they might be willing to sacrifice a lot for the other in this possessive dynamic.
Another common theme is adventure. Writers like to send them on all kinds of exciting adventures, like exploring uncharted islands or facing powerful enemies.
One possible scenario in this fanfiction could be that Ace and Marco are facing a powerful and unknown enemy in a spooky, haunted island. The island is filled with strange noises and dark shadows. Ace's fire powers seem to be ineffective against this new threat as it keeps disappearing and reappearing. Marco, with his phoenix abilities, tries to scout from the air but gets caught in some sort of dark mist. They have to rely on each other and their friendship to overcome their fear and find a way to defeat this mysterious foe.