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.
but after a long time, the Great 
Demon Empire has resurfaced once more.
‫لكن بعد مرور كل هذا الوقت،
Doch nach langer Zeit ist der
Große Dämonenkaiser zurückgekehrt.
pero tras tanto tiempo,
el Gran Imperio Demoníaco ha resurgido.
pero tras tanto tiempo,
el Gran Imperio Demoníaco ha resurgido.
mais après ces longues années,
l’empereur démoniaque est revenu.
ma dopo tutto questo tempo
il Grande Imperatore dei Demoni è risorto.
mas depois de tanto tempo,
но прошло много времени,
и император тьмы возродился.