Nothing about Saitama passes the eyeball test when it comes to superheroes, from his lifeless expression to his bald head to his unimpressive physique. However, this average-looking guy has a not-so-average problem--he just can't seem to find an opponent strong enough to take on!

An emergency summons gathers Class S heroes at headquarters...and Saitama tags along. There, they learn that the great seer Shibabawa left the following prophecy: "The Earth is in danger!" What in the world is going to happen?!