With the Trials of Polaris behind them, Alcor appears before Hibiki and co. and states that he intends on killing Yamato of his own free will and in doing so, entrusting the fate of the world to Hibiki, a battle which Yamato accepts. As their battle begins, Hibiki explains to Daichi and Io what would happen to the world if Yamato has his way after meeting with Polaris. While attacking Yamato with tentacles, Alcor realizes that Yamato had been steadily drawing him closer to the Tokyo Tower to enhance his use of the Ryumyaku. Afterwards, they take a short pause and exchange threats. Alcor expresses his support of Hibiki's future since he was treated as an actual person when with him, although Yamato retorts that Alcor should revert to being a mindless tool, and if so, he would be allowed to see his vision of the future. Just then, they both receive each other's death clips. Hibiki also receives their death clips and decides to keep his promise to Yamato by stopping him.
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.
