Spoiler Summary [Click to show or hide]:
OPM Manga Chapter 4 shows Saitama woke up with his pajamas on, and a huge black hand suddenly grabbed him by his head. He punched it but countered him back, landing a punch on his face, blowing him out of his apartment and leaving the windows destroyed…
His head is bleeding, and after regaining his composure, the pummelling continues while revealing the monsters that claim to be the true people of the earth. They came from the underground, and people call them Subterraneans. They are here to take over the surface due to their rapid increase in numbers.
After a few chit-chats with the Subterraneans, the fighting reignited, and it was surprising that some of them could take the blow of our one-punch hero.
Meanwhile, Saitama was getting pummelled as the Subterraneans started attacking him again. He destroyed some, but he was also receiving damage due to their sheer numbers.
A subconscious feeling started to emerge within him. That is the thrill of the battle that he’s been longing for. Sweaty and with his shirt ripped off, he was the one left standing amidst the sea of corpses.
Suddenly, the Underground King appeared with four hands each of them having a sword. Saitama was excited to fight this ultra-strong monster boss, but when he was about to attack, his alarm went off, and he discovered everything was all a dream. Talk about a rude awakening.
Disappointed, he heard voices claiming to be Subterraneans, but unlike his dream, they were all puny monsters that didn’t have the strength to match him.
Upon arriving at the scene, the monsters retreated underground, leaving a white flag that says “SORRY”.