Despite finally learning more about the "Sunset of the Underworld" a thousand years past, Yuki finds his thoughts returning once more to his former friend and current enemy Kanata . . . But while Yuki may be new to picking sides in a centuries-old war, it is nothing new to the Zweilt. And Kuroto and Senshirou, the new Zweilt pair Yuki has only just encountered, harbor a profound hatred for Opasts, swearing revenge on one in particular. What happened...