High school student Ryouma Mikoshiba is summoned to another world by the warmongering O’ltormea Empire. However, Ryouma is not an ordinary schoolboy; he possesses both talent and training in martial arts. He uses his martial arts skills to escape captivity and swears revenge on the country that summoned him. Ryouma finds himself in a world where he can grow stronger by absorbing the life force of those he slays—a world that suits his talents perfectly. Pursued by the O’ltormean court for killing an important official, Ryouma attempts to flee across the border while keeping his identity hidden. During this escape, he encounters twin sisters, Sara and Laura, an event that will change his fate. Thus begins the epic tale of a young man and his journey of war and domination!