While fleeing with his adoptive father, Shiki Ichinose is attacked by an unknown assailant; he learns he's actually a descendant of the Oni and a target of the Momotaro Agency.

Shiki awakes to find himself before Oni Agency member Naito Mudano, who evaluates Shiki's potential as a valuable addition to the organization.

Mudano splits the new students into teams before the strange game of tag begins, but Shiki soon gets into a fight with his teammate Jin Kougasaki.

Shiki collapses after overexerting himself during his fight with the titan; unconcerned about his teammates, Kougasaki attempts to take down Mudano.

Mudano takes the team on a trip to help the Kyoto base; the Momotaro Agency's Tsubakiri Momomiya and Yomogi Momokusa launch an attack on the Oni; Mudano entrusts the students to Commander Oiranzaka, heading to battle.

Forced to fight their reanimated fallen comrades, the Support Unit finds itself overwhelmed, putting the Kyoto Base at serious risk.