Modern Day Hero is a Manga/Manhwa/Manhua in (English/Raw) language, Action series, english chapters have been translated and you can read them here.
A boy named ‘Hyunsung’, who was denying reality while suffering from school violence, gets into a traffic accident while saving a child on his way home and is summoned to another world. Summoned to the other world he had longed for, his excitement is short-lived as he is immediately sentenced to execution without understanding why. Unjustly killed, Hyunsung does not die but returns to reality, waking up in a hospital. Just when he thought he had returned to his normal life, unidentified monsters begin indiscriminately killing people in front of Hyunsung. An otherworlder, possessing the body of a bully, claims to be a hero. Before Hyunsung can fully grasp the situation, he finds himself needing to save the world. Can Hyunsung defeat the Demon King and restore the original world?