Okutama Personal Labyrinth ~The Encroaching Otherworld Maze 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

"Dungeons are invading Japan! Conquer dungeons of swords and magic with 'modern science'!" A dungeon suddenly appeared in the modern world. And the witches by the magic essence "mana" overflowing from the erosion mouth. A new occupation "Adventurer" is born.