Aiming to Conquer the Demon King’s Castle with Merchant Skills ～Since I Have Been Transported to Another World, I Decided to Survive with the Strongest Items and Talk Techniques ～ is a Manga/Manhwa/Manhua in english language, Comedy 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

One day, Sota, a university student, is summoned to another world! Moreover, after being summoned, he was mistaken for a hero and imprisoned in the Demon King's Castle, where he was in a desperate situation...! Sota gets through the predicament with his natural skill, but for some reason he ends up solving the embarrassing problem of Fafnir, a super beautiful demi-human...!? Win the hearts of the demi-human girls living in Demon King's Castle and aim to escape from Demon King's Castle! A fantasy romantic comedy that opens up a different world with its natural business spirit, begins!