A-City

A-City (A市 A Shi) is a large city within the world of One-Punch Man. It is the location of the Hero Association headquarters. A-City was completely destroyed by the Dark Matter Thieves, so it is now only inhabited by Hero Association staff and heroes. Metal Knight re-built A-city into an expansive headquarters for the Hero Association with highways leading to all other cities.

Inhabitants

 * Sitch

Monsters

 * Skyfolk
 * Sky King (Deceased)

Saitama Introduction Arc
The monster Vaccine Man attacks the city. Lightning Max and Smile Man are sent to defeat him but are defeated. Later Saitama shows up and defeats Vaccine Man with a single punch.

Rumored Monster Arc
The council of the Hero Association call up the heroes to check in on their cities and to see if everything is alright.

Alien Conquerors Arc
Boros and his Dark Matter Thieves attack the city in order to find the worthy opponent of a prophesy that Boros found. Over 99.8% of A City is destroyed in the process. The Dark Matter Thieves were defeated by 6 S-Class heroes, Iaian and Saitama. Metal Knight was contracted by the Hero Association to clear and rebuild A-City, which he did in a week. He focused on turning the Hero Association headquarters into a near-impregnable citadel and left most of the surrounding city as a wasteland.

Psychic Sisters Arc
The A-City headquarters having been remade into a fortress by Metal Knight, at least some of the A-Class and S-Class move there, including Saitama. Since there is still a lot of vacant property within the citadel, some of it is sold to wealthy citizens looking for a safe place to stay.