While on the road to their field trip, Class 2-C's bus is enveloped in light, and the Goddess, Vicius, summons the students and their teacher to another world. The Goddess hopes to raise them as Heroes to defeat the Great Demon Empire, and she welcomes the students after appraising their abilities with her crystal. However, Mimori Touka is appraised as an E-Class, the lowest rank... and he's branded a trash hero.
The reverse summoning ritual requires 
a special element known as demon king essence.
‫يتطلب طقس الاستدعاء العكسي
‫عنصرًا خاصًا يُعرف بجوهر ملك الشياطين.
Das Ritual der umgekehrten Beschwörung
erfordert das Böse Element.
El ritual de invocación inversa requiere
de la Esencia del Rey Demonio.
El ritual de invocación inversa requiere
de la Esencia del Rey Demonio.
Pour le rituel d’invocation inversé,
il faut une essence de seigneur du mal.
Il rituale per rimandarvi indietro
O ritual de invocação reversa requer um elemento
especial chamado Essência do Rei Demônio.
Для обратного призыва