Chapter 4

"Dark Undergrounders" (闇の地底人, Yami no Chisokojin) is the 4th chapter of the One-Punch Man manga series.

Summary
Saitama is asleep in his apartment, but wakes up suddenly when his wall explodes and a hand reaches in and grabs his head. Saitama punches the arm of whoever grabbed him and the hand lets go, but he is then punched in the face, sending him crashing through a wall and down to the street below. When Saitama lands, his forehead is bleeding, but he has hardly any time before a creature pops out of the ground behind him and swings at him, sending him flying even though he attempted to defend, and when he gets up, he sees more of the creatures coming out of the ground. These creatures reveal themselves to be the Subterranean People and intend to take over the world, they surround Saitama and begin to attack him.

Saitama takes one out, but is quickly attacked by another. Saitama then rushes into the group of enemies, fighting madly until all of the Subterranean People are dead at his feet. As Saitama is standing there on the corpses, he hears a voice behind him and turns to see the Subterranean King bursting through the ground and is about to fight him when he hears his alarm clock go off and wakes from his dream. Sitting there stunned and disappointed he hears the Subterranean King yelling outside, so he goes and kicks him in the face, killing him in one hit. He declares that he will protect the surface and is about to fight the Subterranean People, but finds that they have already retreated back underground, leaving a white flag with the words "We're Sorry" on it. Saitama is left severely disappointed.