Something must have been done to the other yus as well, because Marisa and Patchouli haven't really moved, even if they have more control over their faces. Alice is the only one that was able to move enough to have a tantrum. Either that or something else is going on entirely.
The guy beautified the yukkuris and told them hold a "pretty" or "cool" pose.
He poured some glue over the yukkuris because he wanted to create some nice models. The glue turns hot but doesn't ignite, but the other yukkuris can't hold their poses. Marisa tries to lick off the glue, Patchouli barfs, alice just moves around too much and made the glue hotter.
In the end only Reimu was the usable one and she became part of the collectable set.
Maybe she (not he) used cyanoacrylate-based glue to fix these guys' pose into place. This thing can generate a lot of heat and cause burns even for the human skin when they solidify, and become hard and waterproof afterwards. Just imagine how badly can they burn a manjuu's dough coating.