20th Century Boys: Chapter 1 is the first of a trilogy of live-action adaptations of the manga of the same name by Naoki Urasawa, one of the most successful sagas of all time in Japan, with more than 28 million copies sold and published in 13 countries, including Spain.

In 1969, Kenji and his friends wrote the Book of Prophecies, in which they told how an evil organization was destroying the world. Years later, in 1997, a dangerous religious cult and its leader, who calls himself Amigo, talks about the same prophecies that Kenji and his friends wrote as children, and even uses the same symbol they created for their group. The prophecies have begun to come true, and Kenji and his friends are the only ones willing to fight back.