Grim Reaper: Master of the Underworld 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

Jia Gang, the greatest swordsman of Joseon, fails to avenge his master and dies, descending to the underworld. Possessing a special soul, Jiagang is promised a chance for revenge by the King of the Underworld and takes on the path of a Grim Reaper who captures evil spirits.