Strike the Blood, Vol. 15 (light novel‪)‬

The war that changed everything
It's a Valentine's Day that Kojou won't soon forget! Amid the buzz of crushes and chocolate, dark words arrive on the wings of Glenda, the Dragon of the Swamp. Velesh Aradahl is holding Yuiri and Shio captive! And using them as collateral, he challenges Kojou to a vampire duel...At the same time, the Holy Ground Treaty Organization has deemed all of Itogami Island-altar for The Cleansing and domain of Dimitrie Vattler-a global threat. The only way to get the organization to overturn their decision is for Kojou to defeat Vattler and claim dominion of Itogami Island for himself! But can he do it in twelve hours, before the HGTO has the entire island destroyed?!