Nezuko is initially 12 years old in the manga. As the story unfolds, her age doesn't change significantly in a traditional sense, but her character development is quite remarkable.
In 'Ava and Gabriel a love story', it could be that Ava and Gabriel are from different worlds. Ava might be a free - spirited artist while Gabriel is a more reserved academic. But one day, they are brought together by a common friend at a party. At first, they don't seem to have much in common. However, as they start to have conversations, they find that they are both passionate about a certain cause, like environmental protection. This shared passion becomes the foundation for their relationship and soon enough, love blossoms between them.
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.