Touno Hifumi was summoned to another world, to be a Hero for a kingdom. Unbeknownst to the summoners, he's a kill-happy person who restrained his killer instincts with martial arts.
Upon arrival, he slaughters various knights and the mastermind of the event, the King. Unwilling to oppose this strong killer, the Princess let him go free. Thus starts his fun life of travelling the world, unrestrainedly killing any who attempt to kill him.
But first, let's purchase a pair of female slaves.