The Earth of the future. Science has advanced dazzlingly, but people have fallen into mental chaos. Seizing this moment, the eight legendary demons of the Eight Heavenly Generals break their seals and begin to destroy the Earth. To counter them, humans create four Iron Heavenly Kings based on ancient legends. And they find the only four individuals capable of piloting them: the four youths, Gun, Louis, Jean, and Spike. Due to a computer system malfunction caused by an unknown force, they suffer severe injuries during training. Unaware that this is a scheme by the eight demons, Gun and his team blame each other and fail to coordinate properly, even when piloting the Iron Heavenly Kings. In this chaos, they are defeated by the demons, who expand their power, take control of the global computer network, and ultimately destroy the Iron Heavenly Kings' base completely. (Im Jae-won)