I like Paper Mario, and this is like Paper Mario. Plot was cute, though I do wonder why they need to steal money from fairies to buy a ring that only costs $40.
I love the art style. Not just the paper aesthetic, but the fumo-like designs of the overworld sprites, and the way the characters move in the battle art animation. Reminds me of mid-2000s flash games, in a good way. Same with the music-- ZUNpets are always welcome.
One minor nitpick is that the slimes don't seem very... Touhou-like. I think it'd work better if they were some other monster instead, probably something that shoots at you. Or heck, you could reskin the slime into a black ball and say it's Rumia.
For the gameplay, it was okay. I really like how blocking and parrying work. Also, it seems like Youmu's little attack-minigame-timing things are way easier than Reisen's, but Reisen's special move costs less and does more damage. Is that intentional? If so, that's a pretty cool way to differentiate them. Though, I wish there was a little more of that. For example, if Youmu did 2 damage from parrying instead of 1. That said, I like that they share the P meter. Makes 'em feel like a couple, ya know?
In short, 'twas nostalgic.