Curiosity... how common is Yuuka X Aya pairing? ...I want to add it to the "unlikely couples" pool, but I'm really not sure.

Not on the Touhou wiki's list of "common pairings", and I don't believe I've ever seen it before, so into the pool it goes.

HisRotundity said:
Not on the Touhou wiki's list of "common pairings", and I don't believe I've ever seen it before, so into the pool it goes.

A search with the two of them + yuri only gives me one pic of the two of them. So, yeah, pics of the two as a couple aren't common at all.

The_Shadow said:

A search with the two of them + yuri only gives me one pic of the two of them. So, yeah, pics of the two as a couple aren't common at all.

On Pixiv or on Danbooru? That's an OK metric to use here, but not on Pixiv, because it's common to leave out the yuri tag and just use a portmanteau of the couple's names.