Ikebukuro

Ikebukuro is one of the three human cities listed by Shinoa along with Shinjuku and Shibuya. It is controlled by the Japanese Imperial Demon Army.

Details
A city maintained by humans after the Apocalypse Virus killed off most of the human population in the year 2012.

As one of the cities controlled by the Japanese Imperial Demon Army, it is probably similar to Shinjuku and Shibuya. It is most likely surrounded by tall walls to defend them as well as spells to weaken approaching Horsemen.

Society
Ruled by the Japanese Imperial Demon Army.

Nagoya Arc
Shinoa Hīragi lists Ikebukuro as one of the three human cities while discussing how her squad needs to improve.

Trivia
A real place. 
 * Ikebukuro「池袋」 means "pond sack."
 * Not yet shown in the manga and only mentioned thus far.