That Time I Got Reincarnated as a Slime: Trinity in Tempest (Manga) 11

Foss, Stella, and Nemu finally arrive in Falmuth, the royal capital. Originally intending to only observe the coronation ceremony, the three girls find themselves with invitations to the ball as well. Having never participated in such a formal affair before, the girls must first undergo emergency etiquette and dance lessons. Meanwhile, as preparations for the ball continue, a shady individual is hatching a nefarious plot…