The trouble with the Black Death Emperor Faction has been resolved. Kojou has returned to his daily life with Sayaka as a new acquaintance, but he can't decide whether or not he should reveal his vampiric nature to Asagi. It's around that time when he meets a friend of Nagisa's, Kanase Kanon, known as the middle school saint.

Kojou and Yukina prepare to ambush Possession Mask, the group responsible for the attacks around Itogami Island... but one of the Possession Mask members they see is Kanase Kanon.

The deserted island turns out to be a research facility owned by Magus Craft where Kanon's father, Kensei, conducts research. Kojou and Yukina are attacked by a vanguard force, but the one to save them from danger is Princess La Folia of Aldeigia, a young woman with deep connections to both Kanon and Kojou.

When Kojou is disabled in the battle with Kanon, Yukina retreats with him behind La Folia's barrier. Both Yukina and La Folia share their blood with Kojou to aid in his recovery and the awakening of a new power. They have no choice but to rush to Kanon's rescue as her ego slips beyond control and she loses her grip on her humanity.