The Reason Why the Hero of Another World Saves the Earth is a Manga/Manhwa/Manhua in english language, Manhwa series, english chapters have been translated and you can read them here. You are reading chapters on www.mgeko.cc fastest updating comic site. The Summary is

A world where, after the night of Awakening to the System, everyone had mana. And, SuJeong, the only one without mana. He who barely lives by working as a Porter in Dungeons, meets a child who claims to be a soldier from another world. A soldier carrying a mysterious power. The first skill he blossoms as he meets the soldier. Will SuJeong, with this wacky soldier who only remembers his mission of saving the Earth, be able to achieve his goals?