"Yamada: As for me, I never actually had the chance to do much key animation…
Hayashi: You did do that bit in episode 13 where little bits of sweat come flying off Riina as she’s dancing away. That actually turned a fair number of heads; even Akai (Toshifumi) asked around to find out who did it."

https://blog.sakugabooru.com/2016/08/14/the-idolmaster-cinderella-girls-staff-interviews-animators-roundtable/