21st Century Boys

is a manga written and illustrated by Naoki Urasawa.

Plot
Growing older is pretty rough and Kenji is finding out just how hard it can be as life starts wearing down on him. On top of trying to make ends meet running a convenience store he has to care for the niece that his missing sister left in his care. Memories of youth make it easier, until those memories come back to haunt him

Picking up directly after the events of 20th Century Boys, it seems like the world is finally out of danger, but the mystery of "Friend" still exists. As the world is threatened again, Kenji must search his memories for any clue about "Friend".