Ernak is a Manga/Manhwa/Manhua in english language, Shounen 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

Novice gamer Youngsik Yuu, who finds himself sucked into a game world several years in the past, attempts to make the most of his wealth of knowledge, to survive in a world unwittingly bracing for a huge war.