Strike The Blood, Vol. 4 (Manga)

At the invitation of Dimitrie Vattler, emissary of the First Primogenitor, Kojou and Yukina attend a yacht party. Dimitrie''s guardian has it in for Kojou, and as though that''s not bad enough, the festivities turn serious when Kojou and Yukina discover a terrorist plot that threatens Itogami Island itself...