Yukihiko Tsutsumi's hit "20-Seiki Shonen" ("20th Century Boys") trilogy is based on one of those "what if" premises that may look almost childishly obvious, but, from a commercial standpoint, is simply brilliant.
In 1969 a gang of small boys write down disastrous "predictions" about the future that read like steals from the era's monster and SF movies, concluding with the end of the world. So far, so innocuous.
Kenji (Toshiaki Karasawa), the leader of the gang, grows up to become a failed pop musician and full-time convenience-store manager, while caring for his sister's baby girl, Kanna. Then, in 1997, the "predictions" start coming true, with the help of a shadowy cult led by a masked man known only as "Tomodachi" ("Friend"). Kenji becomes determined to stop the cult and enlists the help of his boyhood pals.