Jack is a samurai warrior, whose magical sword is enchanted "with the power of righteousness," who trains his body and his mind to confront Aku. Aku is an evil, shape-shifting wizard who dethroned Jack's emperor father. During their pitched battle, Aku dispatches Jack into the future through a time portal. The solitary warrior's single-minded quest is to find his way back to undo the devastation of Aku's tyrannical rule.