Embodiment of the Assassin in the Murim World is a Manga/Manhwa/Manhua in english language, Action 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

No.1 Assassin Kim Gun falls into the world of Murim due to a mysterious accident. In order to return to the Earth from which he came from, he learns that he must complete the mission of "conquering Murim". With two guns, Kim Gun's adventure to settle the unfamiliar world of Murim begins.