What happens when a superhero can beat the snot out of every villain with just one punch? Can he find an opponent to give his life meaning, or is he doomed to a life of superpowered boredom? 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!

Garo, a man who admires monsters, attacks the Hero Association! But after pulverizing the heroes there, he just leaves. What the heck does this guy want?! Meanwhile, Class-B, Rank-1 Miss Blizzard visits Saitama at his apartment. Since he's just a low-ranking hero, she thinks she can make him one of her subordinates, but as always, Saitama has other plans!