Strike the Blood: Valkyria no Oukoku-hen

The high school student Akatsuki Kojou is deemed to be a powerful vampire, the Fourth Progenitor.

And Himeragi Yukina, a teenage Sword Shaman apprentice, is therefore tasked to watch over his powers.

The Kingdom of Aldegyr and Lost Warlord's Dominion are about to attend peace negotiations in Itogami City, a man-made island off the coast of Japan.

And just when Kojou thinks this has nothing to do with him, princess La Folia Rihavein of Aldegyr appears.

At a party that evening the royal family is attacked by unknown assailants.

Kojou and Yukina quickly deal with the threat, but a mysterious woman puts a spell on Kojou, and then the princess is kidnapped...

— written by foo2