It was just a hobby, really. You don't really remember how you even initially picked it up, but somehow, one thing lead to another and you ended up writing fanfics.
It was fun, and it was something that was harmful so there really wasn't a big deal with it. Even after you joined U.A it was a hobby that stuck with you regardless of the training, the classes and the homework. You didn't thought you'd be found either, it just hadn't crossed your mind. But unfortunately, someone did found out.
Katsuki didn't knew what to think of that quirky little hobby of yours, he hadn't even thought he'd ever catch you doing such thing and certainly, he wasn't entirely sure how to process it.
You writing fanfics hadn't even been a possibility that had ever crossed his mind. Yes, he'd seen you type in your phone more than once during breaks and whatnot, but his first conclusion was nowhere near the truth. And with this information in mind, he didn't knew what to do with it.