Strike The Blood Vol. 13 (Light Novel)

Kojo Akatsuki is, at first glance, an ordinary high school student at Saikai Private Academy on Itogami Island, a man-made island south of Japan that is a sanctuary for monsters and demons. However, there’s something different about Kojo: he is suspected of being a powerful vampire known as the Fourth Primogenitor who has the potential to disrupt the balance of power in the world!
Yukina Himeragi is an apprentice Sword Shamen from the Lion King Agency who is sent to observe Kojo and eliminate him should he prove to be a threat. Taking her role as observer very seriously (perhaps too much so), she moves into the apartment next to him and begins following him everywhere. However, she soon realizes there is more to the situation than she first thought, and unbeknownst to her, there are threads of fate that bind them together as she eventually begins to develop feelings for him in this supernatural action light novel by Gakuto Mikumo and Manyako.
The Roses of TartarusItogami Island has become completely cut off from the mainland, and mysterious murders are happening one after another. The culprits appear to be Tartarus Lapus, a group whose goal is the destruction of the demon sanctuary. Meanwhile, Nagisa is still recovering and meets a strange girl named December who, unbeknownst to Nagisa, is the leader of Tartarus Lapus and possesses a special ability that rivals even Kojo’s power!
Notice: This light novel is written in Japanese.