At the end of the 21st century, humanity is facing the worst. It was the emergence of monster people. Kaijūjin, or "monster people," are the last of the human race that has been transformed into monsters. They have completely lost their human nature, and are ferocious and brutal, with a variety of monstrous abilities that threaten to bring humanity to the brink of extinction. But there is only one person who stands in the way of these terrifying monsters!