SEN-DO-KAI.Zak, Chloe, Kiet and Fenzy are four 13-year-old friends who are not very popular and have no talent for sports. One day, while they lament the rejection of their classmates, lightning strikes from the sky with four bracelets and transports them to another dimension where they have super-powers. There and Tänpo awaits them, a small and wise being who mistakes them for some warriors whom he intended to train in the art of "Sendokai". After testing his skills, Tänpo finally discovers that there has been a mistake and the boys are not the warriors he expected. He asks them to leave, but Zak is fed up with others judging them and decides to prove himself to him. Although the test is again a disaster, Tänpo senses his fighting spirit and rethinks his decision. Ultimately, he decides to train them to be Sendokai warriors. When they are, they must fulfill a mission: save the Earth from the invasion of the Zorn Empire.