Demon king reincarnated as a hero

Demon king was defeated by the heroes and then got reincarnated as a human into a world called earth . At first he thought he became a mere human and above all he became a commaner but as time passed he got used to this life and was living peacefully but on the first day of his highschool he's whole class got summoned to another world and a sweet voice greeted them saying " Welcome heroes" This novel will update on Monday only I am just a highschool girl and my English is not that good