Kazuma Nakao.
Nakao actually also animated Miiko's cover of Momoiro Clover Z's Chai Maxx Zero in episode 1 (not uploaded on booru), but due to episode length it was not all used. This animation was based on that cut Nakao did in episode 1.

My goodness, that looked super smooth.

Correction: The base animation was Kazuma Nakao's work, but Kozue Horanai did draw this scene where Ariel's imitating her Mom's dancing. In a way, that's what Horanai did too (imitating Nakao's animation). Both Horanai and Nakal should be credited I think.

Note: Nakao did the scene where Miiko came back to the stage and grabbed the mic back from Kano.