The Rumored Monster Arc is the second arc of the Hero Association Saga and the fifth arc in the series.
The Hero Association staff are having a meeting, discussing reports from various cities. The association sends Spring Mustachio and Golden Ball to investigate rumors about the abandoned section of Z-City. They encounter Kombu Infinity, who defeats them. The monster informs them that it isn't the rumored monster, but seeks to become the monster for fun. It encounters Saitama, who steals its kombu hair to make soup. Genos believes Saitama is trying to regrow his hair with the kombu, but Saitama firmly denies it.
- The existence of the Monster Association is hinted at for the first time.
- It is revealed that the Hero Association leaves certain heroes in-charge of certain cities.
- Sneck is in-charge of F-City, Mushroom and Horse-Bone are in-charge of H-City, Lightning Genji is in-charge of D-City, Heavy Kong is in-charge of W-City and Watchdog Man is in-charge of Q-City.
- Genji mentions that B-City and D-City are still being repaired after Marugori's attack.
- Sneck is spying on Hammerhead, who is looking for a job.
- Kombu Infinity vs. Golden Ball and Spring Mustachio
- Kombu Infinity vs. Saitama
- The Rumored Monster Arc is the first original Manga story arc.
|Introduction Saga||Saitama Introduction Arc • House of Evolution Arc • Paradise Group Arc|
|Hero Association Saga||National Superhero Registry Arc • Rumored Monster Arc • Giant Meteor Arc • Sea Monster Arc • Alien Conquerors Arc • King Arc|
|Human Monster Saga||Garou Introduction Arc • The Blizzard Group Arc • Hero Hunt Arc • Monster Raid Arc • Super Fight Arc • Monster Association Arc|
|Neo Heroes Saga|
|Rumored Monster Arc|
|Fights||Spring Mustachio and Golden Ball vs. Kombu Infinity|