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

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...!?