Hibiki and the rest of the summoners fights against Megrez that have appeared simultaneously in Tokyo, Osaka, and Nagoya. However, Megrez will continuously revived unless the three main bodies are defeated at the same time. As the battle starts, Hibiki and Io summons their demons, along with Hinako who uses Berserker to avenge Keita's death, while Yamato uses his power that increased by the Ryumyaku tower and his demon Baal to stop Megrez' movement until the right moment. During the battle, Hibiki and Io received Ronaldo, Joe, and Otome's death clip that shows them died by Megrez' attack. Hibiki immediately tells Ronaldo to escape, but Ronaldo, Joe, and Otome decides to keep fighting since there are no summoners other than them that can defeat Megrez and resolves to avoid their fate like Hibiki does yesterday.
The countdown to extinction begins on Sunday with the arrival of the Septentriones, otherworldly invaders set on the eradication of mankind. Caught in the crossfire, Hibiki Kuze and his friends join in the war for humanity's survival by signing contracts with demons to become "Devil Summoners." Soon, their abilities attract the attention of JP's, an underground agency led by Yamato Houtsuin. Once recruited into JP's, Hibiki and his friends fight and bond alongside other ordinary citizens who are Devil Summoners.
However, with each new day, another Septentrione appears to wreak havoc upon Japan. Even if many lives are lost in the process, before that night ends, the young summoners must defeat the invaders at all costs.
