I know and accept that 98% of Touhou Shipping, or even just saying a Touhou gal is gay, is just head canons and the like. The other 2% are whatever Renko and Merry have going on
But like... here is Reimu, thinking she's being flirted with by another woman. She is blushing, and flirting back. There is simply no heterosexual explanation for that.
There's actually a post on tumblr that goes into how the "official-ish" translation of this convo isn't very good, and the original is actually EVEN GAYER. Check it out!