Rather than dealing with the inappropriate 'twerking for him sex fanfic', we could shift to a story about a fitness class that includes twerking as an exercise. People are there to get fit, have fun, and build confidence through this energetic dance form, without any inappropriate elements.
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.
Sure. 'Twerking for him' could be seen as dancing in a twerking style specifically for someone in a non - sexual, performance - based way. For example, a dancer might twerk as part of a show dedicated to a friend or a family member, just to show off their skills and bring a smile to their face.
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.