While assaulting a Shuuki nest, the 7th Squad are confronted by a mysterious girl riding atop Unihorn, Kyouka's sworn enemy. Who is she, and why does she seem to recognize Yuuki? There's no time to ponder that mystery, however, as the leaders of the 6th Squad-including Himari's sister- arrive for joint training! The stage is set for a grudge match between the two siblings, and Himari drafts the Squad's slave-cum-caretaker to help. Not that Yuuki's complaining-more masters means more sweet rewards!