Boushoku-Hi no Ken is a Manga/Manhwa/Manhua in (English/Raw) 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

After Dean, a third rate adventurer, got surrounded by demonic beasts in the demonic labyrinth, he fled to a place where he found the strongest demon who devours power: The demon-fed sword Belzera, born to the Gluttony Empress Belzebuth. After obtaining such unexpected power, he once again aims to become a first rate adventurer he looked up to, and delves deeper into the labyrinth. However…