I don’t know much about Touhou, but aren’t Maribel and Renko not from Gensokyo? Is this an alternate universe thing then since Aya and Hatate are there too? Anyway, this was pretty good and, I guess, a unique concept too, so that was interesting.

I don't know much about Touhou either, but I think Aya may have to go to the outside sometimes. Aya has a alternative form that disguise her as a human journalist. If she doesn't need to deal with humans how is that necessary?

The outfit:

https://danbooru.donmai.us/wiki_pages/shameimaru_aya_%28newsboy%29

It's for going to the human village inside Gensokyo. I'm not aware of her going to the outside world canonically.