I Won't Spare Any Hamenrudah! A New Magical Battle Maiden Transforms - S1.E1

Rin is a shy, ordinary girl, worried because her breasts are slightly bigger than other girls’. One day, she is attacked by an evil organization but saved by Magical Valkyrie Frostia, a magical girl superheroine. When she discovers Frostia’s true identity, Rin joins her as a Magical Valkyrie to fight against evil.