Shiki learns he's an oni when attacked by Momotaro.

Oni Agency member Naito Mudano retrieves a wounded Shiki and begins evaluating him, determining if he is fit to join the Agency. However, Shiki only wants to avenge his father. Mudano switches to a harsher test, and Shiki goes berserk. In the chaos, Shiki manages to control his Oni blood and is granted admission to Rasetsu Academy where Mudano teaches. Shiki enrolls, vowing to become stronger.

The first test the boys face to enter the academy is playing "Oni Tag."

If they want to pass the test their teacher has given them, students must work together.

The students reach the Kyoto underground and discover new things about the war they are involved in.

The undead attack the students and Shiki is forced to make a decision that will change his mind.