The Demon King's Cowardly Vessel

Remember when you were young, and your parents told you not to touch things that weren't yours?Well, Juin should have listened to that piece of advice before he touched an antique sword in a museum.Juin, an average human from Earth; a thin, well-known weakling who was afraid of his own shadow and was basically everyone’s favorite punching bag.One day, he accidentally summoned a demon from another world. And the worse part was… He summoned a demon king who had the emotional maturity of a teenager and the mouth of a sailor.With Juin's fear of basically everything and the arrogant demon king who was afraid of nothing, what would the 16-year-old's life be from now onward?