After defeating Boros and his army, Saitama returned to his normal life in Z-City, but the Hero Association faced a growing problem: increasing monster sightings straining their resources. To address this, they considered enlisting the help of unorthodox fighters, including hoodlums. During the initial meeting, a man claiming to be a monster appeared and began attacking the crowd, introducing himself as Garou. Garou's identity as a former student of Silverfang and his unrelenting assault on heroes made him a formidable foe. Saitama, intrigued by this new challenge, joined the martial arts competition to capitalize on the opportunity. Meanwhile, a new global threat emerged, potentially fulfilling the prophecy of Madame Shibabawa.