Imagine a Gacha Club character that was created by a player who then abandoned the game. This character was all alone in the game world. It had no purpose as the player who was supposed to guide its story was gone. It would watch other characters having fun with their players, and it just felt so left out and sad, like it was a forgotten entity in the Gacha Club universe.
One sad story in Gacha Club could be about a little cat - like character. This character had a dream of becoming a famous singer in the Gacha Club world. It practiced day and night, but when the big audition came, it got really nervous. And due to a technical glitch, its voice didn't come out right during the performance. Everyone laughed at it. After that, it lost all its confidence and hid away, too ashamed to face others again.
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.
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.