In "One Punch Man," Volume 1, we follow the extraordinary life of Saitama, a seemingly ordinary man who possesses an extraordinary power - the ability to defeat any opponent with a single punch. Frustrated by the lack of excitement and challenge in his hero career, Saitama battles an existential crisis as he struggles to find an adversary capable of putting up a real fight.

As a hero for fun, Saitama encounters a series of increasingly powerful and bizarre villains, all of whom he dispatches effortlessly, leaving him feeling unfulfilled and trapped in a monotonous cycle of overpowering his foes. Despite his incredible strength, Saitama yearns for a challenge that will restore purpose and excitement to his heroics.

Vaccine Man is the first villain Saitama encounters in the series. He's a monstrous creature who claims that humanity's pollution and destruction of nature have pushed him to eliminate humanity. However, Saitama swiftly defeats Vaccine Man with a single punch.

The second villain, Marugori, is a massive and muscular villain who seeks revenge on society after his brother becomes a hero and dies due to excessive training. Marugori transforms into a colossal, towering giant, wreaking havoc on the city. Saitama steps in to confront him, and with a single punch, Marugori is obliterated.