The third season of One Punch Man. Saitama is a hero who only became a hero for fun. After three years of "special training," he’s become so strong that he's practically invincible. In fact, he's too strong—even his mightiest opponents are taken out with a single punch. Alongside Genos, his faithful disciple, Saitama performs his official hero duties as a member of the Hero Association. One day, monsters claiming to be from the Monster Association suddenly appeared, taking a child of Hero Association executive hostage. The S-class heroes gather and plan a raid on the Monster Association hideout to rescue the hostage. Meanwhile, Garou, a "human monster" who was taken by the Monster Association during a battle with the heroes, awakens in the Monster Association hideout.

Despite occasional setbacks, Operation Strix has remained on track to extract sensitive information from the enigmatic politician Donovan Desmond. To this end, spy Loid Forger has managed to maintain his pretend family consisting of his telepathic daughter, Anya; assassin wife, Yor; and their clairvoyant dog, Bond. Still the only one aware of everyone's true identities, Anya tries to sustain the family's cohesion while working to befriend Donovan's son Damian, her Eden Academy classmate. However, Anya's efforts instead earn her another Tonitrus Bolt, bringing her closer to getting expelled and jeopardizing the operation's success. Hearing the news, Loid faints from shock. In his unconsciousness, he reminisces about his tragic past and his journey to becoming a spy. Realizing what Operation Strix means to him and the world, Loid finds renewed motivation. Although they each work toward their own covert goals, the Forgers continue to cherish their chaotic yet blissful family life.

The appearance of "quirks," newly discovered super powers, has been steadily increasing over the years, with 80 percent of humanity possessing various abilities from manipulation of elements to shapeshifting. This leaves the remainder of the world completely powerless, and Izuku Midoriya is one such individual. Since he was a child, the ambitious middle schooler has wanted nothing more than to be a hero. Izuku's unfair fate leaves him admiring heroes and taking notes on them whenever he can. But it seems that his persistence has borne some fruit: Izuku meets the number one hero and his personal idol, All Might. All Might's quirk is a unique ability that can be inherited, and he has chosen Izuku to be his successor! Enduring many months of grueling training, Izuku enrolls in UA High, a prestigious high school famous for its excellent hero training program, and this year's freshmen look especially promising. With his bizarre but talented classmates and the looming threat of a villainous organization, Izuku will soon learn what it really means to be a hero.

In the beginning, an "orb" is cast unto Earth. "It" can do two things: change into the form of the thing that stimulates "it"; and come back to life after death. "It" morphs from orb to rock, then to wolf, and finally to boy, but roams about like a newborn who knows nothing. As a boy, "it" becomes Fushi. Through encounters with human kindness, Fushi not only gains survival skills but grows as a "person". But his journey is darkened by the inexplicable and destructive enemy Nokker and cruel partings with the people he loves.