Rust is a Manga/Manhwa/Manhua in english language, Manhwa 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

러스트 Ha Maru, a butcher working at a livestock company, is invited by his supervisor to go on a business trip to Japan. However, he soon discovers that the place he has been sent to is a criminal organization run by the Yakuza. In order to survive in this dangerous environment, Ha Maru struggles and gradually awakens his hidden talent for using knives. The butcher, who has now set foot in the underworld, challenges the pinnacle of the criminal world to stay alive.