Syakkin Daiou wa Maou o Taosu! is a Manga/Manhwa/Manhua in english language, SUGGESTIVE 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

Leo goes into an unknown place. Suddenly the demon beast attacked him. After defeating the demon beast, he became a hero! However, in order to get the money back, they will go in an effort to defeat the devil!