One common theme is protection. Since Nezuko is a demon and Zenitsu is a demon slayer, there are often stories about Zenitsu vowing to protect Nezuko from other demon slayers or more dangerous demons. Another theme is friendship. They develop a unique bond in the original story, and fanfics often explore that further, like how they support each other through tough times. And of course, there can be a bit of a romantic undertone in some fanfics as well.
One popular 'zenitsu x nezuko fanfic' is 'The Unlikely Bond'. It beautifully portrays the relationship between Zenitsu and Nezuko. The author does a great job of showing Zenitsu's protective nature towards Nezuko and how Nezuko's presence calms Zenitsu in his often-fearful state.
A simple Nezuko and Zenitsu fanfiction could be that they go on a journey together. Along the way, they encounter other demon slayers who are initially skeptical of Nezuko. But Zenitsu stands up for her, explaining that she's different. This shows the depth of their friendship and how Zenitsu has come to trust Nezuko completely.
Definitely not. In the manga, there's no such plotline of Zenitsu and Nezuko getting married. Their relationship is more focused on being comrades in the fight against demons rather than a romantic one leading to marriage.
There is a 'zenitsu and nezuko fanfic' titled 'Under the Cherry Blossoms'. In this story, the setting is under beautiful cherry blossom trees, and it's a really romantic take on their relationship. Zenitsu is shown to be very shy yet determined to be close to Nezuko. Another one is 'Nezuko's Soft Spot for Zenitsu'. It shows how Nezuko, despite being a demon, has a special place in her heart for the sometimes - comical Zenitsu. These fanfics are great reads for fans of the two characters.
Well, a lot of it has to do with the potential for character development. In the original story, their interactions are limited, but in fanfics, authors can explore how they would grow closer and influence each other. For example, Zenitsu could become more confident because of Nezuko, and Nezuko could learn more about the human side of relationships through Zenitsu. It's also about the fans' love for the two characters and their desire to see them in different scenarios together.
A Nezuko and Zenitsu fanfiction might explore the concept of Zenitsu teaching Nezuko about the human world. Since Nezuko has been a demon for a while, she may have forgotten some aspects of human life. Zenitsu could show her simple things like how to enjoy a flower's beauty or the taste of human food (in a non - harmful way for her). This could create a really sweet and heartwarming story as they bond over these new experiences.
Definitely not. The story doesn't depict Zenitsu and Nezuko as a couple. Their paths in the manga are more about their individual quests and battles against evil.