College student Souji Miyamoto ends up getting transported to another world after swinging a replica sword he bought on impulse. Arriving in the middle of a kingdom's hero-summoning ritual, Souji is mistaken for the Hero.

By a strange turn of events, the princess discovers that he isn't a real hero. Told that he'll get executed if others find out he’s an impostor, Souji is forced to set out on a journey to defeat the Demon King. However, the members of the hero's party all seem to have their own eccentricities...!?