Chapter 20

Spring Mustachio and Golden Ball are sent to comb the fringes of Z-City, noting along the way how monster numbers there keep climbing. Back at Hero Association headquarters, staff track investigations across the regions: Q-City ranks as the deadliest for its swarm of creatures, though Watchdog Man handles his patch without trouble, while W-City, H-City, and D-City report calm. In F-City, Sneck has located Hammerhead and plans to dig deeper. Z-City's count stands out as far higher than anywhere else. Out in the ghost town, the two heroes sense a presence and come upon Kombu Infinity.

Golden Ball opens with a shot that the monster brushes aside before slamming him through the pavement and knocking him cold. Spring Mustachio holds his own for a time, parrying blow after blow and unleashing his Tomboy technique, but Kombu Infinity slips past it. Calling for backup, Spring Mustachio is eventually overcome. The creature reveals it had come chasing the same rumor of strong monsters gathering, only to decide it would become that rumored monster itself. As Blue Fire heads to reinforce, and with no one left to fight, Kombu Infinity resolves to move on to a populated district, only to run into Saitama and fall in a single strike. Elsewhere, shadowy figures speak of the elite monsters dwelling in Z-City. At home, Saitama cooks kombu soup from the hair he took, and flies into a rage when Genos mentions the rumor that eating it will not regrow hair.

Spring Mustachio and Golden Ball investigate the outskirts of Z-City as the Hero Association reviews monster activity across the cities. The two A-Class heroes encounter Kombu Infinity, who defeats them both after revealing his choice to become the rumored monster of the outskirts. Saitama then finishes Kombu Infinity off in one blow, sparing his life but taking his kombu hair. A silhouette of the elite Z-City monsters is teased, and Saitama loses his temper over Genos's remark that the kombu will not cure baldness.

Titled Rumor, the chapter released in two parts, on December 28, 2012 and January 17, 2013, spanning forty pages, with Golden Ball and Spring Mustachio sharing the cover. VIZ Media rendered the title as The Rumor. It belongs to Volume 3 and adapts into Episode 6 of the anime. It stands as the first chapter created originally for the manga rather than the webcomic. Within the run it follows No Time for This and precedes Giant Meteor.