Hibiki, Daichi and Io are arrested by the JPs and brought to a secret underground base located at the National Diet Building. Here, Commander Makoto Sako, explains to Hibiki that the JPs protects Japan from "paranormal anomalies" before she introduces the JP's Chief, Yamato Hotsuin who says that Hibiki's demon Avatar: Byakko is unique, being one of the four symbols of the Chinese constellations. Furthermore, he explains that the Dubhe was only one of 7 creatures called the Septentriones, each of which will appear in the next six days and should the JPs fail to defeat them then the world will disappear. As the JP's scientists begin to analyze the demon summoning app, Hibiki ponders on Yamato's words. The following day, Makoto releases them by taking them to an emergency shelter in Chūō. Here, it is discovered that a rumor of demons running amok is spreading. As Hikibi looks around at all of the refugees in a church, a winged-demon attacks and Hibiki summons Byakko to protect them.
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.
