Aku is the main antagonist of the TV series Samurai Jack and Samurai Jack's arch-nemesis. Aku is a powerful wizard demon capable of shape-shifting and sorcery. Aku first clashed with Samurai Jack when it went on a rampage of destruction, ultimately taking over the empire of Samurai Jack's father. During their first fight, Aku used a time portal to send him forward in time. When Samurai Jack reappears, Aku had already overtaken the world with his darkness. While Aku is treated as a truly serious, dangerous foe, he has shown to be snarky and over-the-top at times.