National Superhero Registry Arc

The fourth arc of the series and the first of the Hero Association Saga follows Saitama and Genos as they formally register as professional heroes. It establishes the class-based structure that will frame the rest of the story, sorting the flawless Genos into S-Class while Saitama, undone by a written exam, lands at the bottom of C-Class despite superhuman physical results.

Saitama breezes through the registry's fitness trials, shattering every record and stunning the other applicants, yet his mediocre written score drops him into C-Class while Genos earns a perfect mark and an S-Class placement. At the follow-up seminar, the veteran hero Sneck bristles at Saitama's indifference and even threatens his standing, though his colleague Jinzuren warns that the newcomer could soon eclipse him. Sneck later confronts Saitama in the open, only to end up planted headfirst in the dirt.

Settling into their partnership, Genos moves into Saitama's apartment and studies his every habit for the secret to his strength. When Saitama learns that inactive C-Class heroes are dropped from the roster after a week, he scrambles across town hunting for any deed to perform. His search is cut short by a returning Speed-o'-Sound Sonic, who hurls a blade and demands a rematch.

Saitama shrugs off Sonic's assault, snapping the assassin's sword with his teeth, but the ninja escalates by knocking out the interfering Tanktop Tiger and unleashing an explosive barrage across the district. After rescuing a child from the wreckage, Saitama finally strikes Sonic down, hoping the incident counts toward his weekly quota. The pair are now officially enrolled, with Genos in S-Class and Saitama at the foot of C-Class, and Sneck has joined the growing list of those who have felt Saitama's power firsthand.