Unparalleled Peril

The Ancient King of the Terror Lizard Clan emerges, prompting Tatsumaki to answer the call and finish the creature by dropping a meteor from orbit. At his dojo, Bang recounts to Saitama and Genos how his finest former pupil, Garou, turned violent and crushed the rest of his top students. A staff member then interrupts to announce a declared emergency, summoning every S-Class hero to a meeting. There Saitama meets the arrogant Atomic Samurai and the rest of the ranking heroes, and Sitch opens the gathering by warning that survival is far from guaranteed. He reveals that the seer Madam Shibabawa, whose forecasts always proved perfectly accurate, choked to death mid-prediction, leaving behind a note reading that the Earth is in trouble and a warning to brace for conflict within six months.

The headquarters is promptly attacked by the Skyfolk, who are slaughtered by Melzargard of the Dark Matter Thieves as an alien ship devastates A-City and inflicts heavy casualties. Iaian, Atomic Samurai's student, engages Melzargard to save civilians, but the monster shrugs off every blow through regeneration and costs Iaian his left arm before his master intervenes. Metal Bat, Bang, and Puri-Puri Prisoner join the fray, the latter surging into Dark Angel form. While the other heroes debate how to bring down the vessel, Genos notes that Saitama has already boarded it and torn through swaths of aliens. Saitama destroys the alien Groribas with one punch and presses deeper into the ship, unaware that Boros waits on his throne.

Shibabawa's death and her prophecy set the coming crisis in motion, and the Dark Matter Thieves' assault marks the start of the alien invasion. Many S-Class heroes make their debut at the summit, Iaian loses an arm to Melzargard, and Saitama begins carving through the enemy ship, with Boros revealed in the closing shot.

Several moments are original to the anime, including Tatsumaki's confrontation with the Ancient King, the argument between Metal Bat and Tatsumaki, and the base scene with the Bearded Worker. The manga never showed Garou beyond mentioning his name, and Iaian's encounter with Melzargard played out differently there, with the swordsman calmly rising from rubble and being ambushed rather than rushing to protect a father and son.