I came up with a concept for a short ecchi story recently. I'm not much of a writer, so I'm just going to write an outline. If someone else wants to pick it up, be my guest.
My story plays off the idea of "Nobody recognizes Reimu without her accessories."
It begins with Reimu in the Human Village, visiting a Hot Spring, or something.
Technically she could be down in Former Hell too, but you'd have to get a bit more creative.
As Reimu is entering the Sauna, after getting undressed; another girl walks in. This other girl looks just like Reimu. Same Hair, same Eye Colour, similar height, etc. Though it'd be fun if she was a bit more, well endowed than the real Reimu.
For example, the real Reimu would be closer to ke-ta style (this artist
>>2923786), while this other girl is more like pic related.
So this other girl see Reimu exiting the room, and sees her clothes sitting in a basket, and puts two and two together. Reimu's in the other room, and these are her clothes.
For one reason or another, she decides to put on Reimu's clothes. Maybe the other humans always remarked that she looks similar to Reimu, and she wants to see for herself, by dressing as her, or something.
She puts on Reimu's clothes, and bam, looks exactly like her, save for the top being a little too small for some reason.
Then, another villager rushes into the changing room. There's been a Youkai sighting, and they were looking for Reimu to help deal with it!
Good thing they found her, better bring her along, right away!
Sometime later, the real Reimu comes back into the changing room, to find the room devoid of any clothing to wear.
For plot reasons, she decides her best course of action is to head out into the village, whilst completely naked.
I'm running out of room now, but from there, there's lots of directions to take the story.
You've got a naked Reimu sneaking around, but if she's caught, people likely won't know who she is, especially since there's an imposter Reimu around town already.