Y-City

Y-City (Y市, Y Shi) is a large city within the world of One-Punch Man. Child Emperor's Lab is located in this city.

Child Emperor's Laboratory
A laboratory owned by Child Emperor is located in Y-City. He builds and experiments with various gadgets here. He is seen sitting on his movable chair.

Restaurant Mammoth
A gourmet restaurant where Fubuki brought Saitama, Genos and King (it is unknown if Bang came too). It seems to have quite a large menu, which includes; Salads with dressing, sirloin, fillet and butter topping.

Heroes

 * Child Emperor
 * Great Philosopher

Monsters

 * Jumping Spider (Deceased)
 * Pluton (Deceased)

Monster Raid Arc
During the Monster Raid, Eyesight attacks Y-City. Pig God defeats her by devouring her whole.

'''The following section contains Webcomic spoilers. You have been warned, manga-only readers.'''

Fall of the Hero Association Arc
The Forest Tribe attempts to invade the city, only to be stopped by Genos.

Numbers
Y-City is attacked by Jumping Spider, but he is quickly put down by Bang, Genos, and Saitama. They then go to 'Mammoth Restaurant' to have dinner.