Rei Zero
Genres: Hentai
Type: OVA, Episodes: 2
Aired: Jun 26, 2010 to Apr 1, 2011
Studio: Anime Antenna Iinkai
Source: Visual novel
Rating: Rx - Hentai
Synopsis:
Tokyo fell into ruins following the consecutive great earthquakes of 2014. As a result, the new city center is built in the location of the former Nishitokyo. Meanwhile, Shinjuku and the submerged Minato wards devolved into slum areas. Further, due to the Immigration Laws of 2040, these slums saw an influx of refugees, mafioso, and terrorists, and is now the leading crime capital of the world. 

The year is now 2049, and this is the stage in which two women embark on an operation to arrest a dangerous drug dealer. 

(Source: translated and adapted from official site by Cranston)