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 four years ago to inspire such loathing? As Yuki bears witness to the flames of revenge that burn in the hearts of those around him, how will his own heart respond to the betrayal that he cannot forget?