Shu pediu as contas de seu emprego antigo para começar sua própria empresa, mas está sem um tostão. Ele sobrevive graças à caridade de Akino, sua antiga namorada e ex-colega de trabalho, e de Kisara, uma jovem colegial que trabalha em sua companhia. Sua sorte muda quando surge um novo trabalho para exterminar uma Ameaça-D de nível médio, e que misteriosamente lhe desperta o interesse.

The evidence gathered points to the real Demon Agent. And it was Shu's most trusted person. As the Police Agency and top officials of AAA continue to strategize and negotiate, Shu confronts the true criminal alone. Why? For what reason? All words and all questions are in vain when the real criminal transforms into a vicious demon right before his eyes. Its power is so overwhelming that, even with AAA's fighting strength concentrated, there is no damage. At this rate, all the people Shu cares for will be hurt. With raging anger and profound sadness in his heart, Shu decides to offer all his precious memories to Kisara. All for the sake of defeating the demon.

Shu is always in trouble with money but manages to live thanks to the support given by his ex-girlfriend Ayano and the ever-devoted Kisara. The same goes for his job as a PMC. With Ayano's cooperation, Shu won a bidding war at a discounted price to participate in the "D Hazard" prevention operation that occurred in a casino. At the scene of the demon extermination, he planned to rely on Kisara's demonic powers, but she is nowhere to be found due to the money situation ruining her mood. As a last resort, he works with Ayano's leading, major PMC and confronts the Demon, but bit by bit, the battle becomes something suspicious...