You would look up into the sky...at the red moon, a winged silhouette barely visible upon it over the ominous mansion in the center of town...
Slowly the moon would draw closer, threatening the whole world, the silhouette seemingly calling it down...
And as the world darkened, the shadow calling the moon would call out to you, and all you could think of was the soft laugh and the unflinching face of the one who sent you on this quest, who uttered the same words what felt like an eternity ago, but was in reality only three days...
"You've met with a terrible fate, haven't you?"
...Or Kokoro would send you on a long subquest to trade masks and stuff to get her more masks. What a manipulative little...
Plus, it sort of makes sense. The mask salesman's emotions are kinda mixed up. Happy, angry, sad...so I guess Kokoro would become more expressive at the expense of becoming bipolar and rarely able to have her upper and lower face exactly match the emotion she's trying to convey. If the other way around, then Kokoro really had everyone fooled by not showing her face's emotion. But which form is Kokoro's real form? Salesman or menreiki? Who knows...
What if Reimu wasn't Shinto all along, she was actually a pastafarian?