Kaijin no Karshel: What a Beautiful Sanctuary

The world ended on the day that the abnormally distorted, super-sized "Great Engine Clock" stood over the entire planet like a tombstone.
The cyberzombies groaned and devoured the few lives that survived, and the last "people" left in the world were a young man named Kyrie and a young girl named Genevieve. The two continue their journey together and at cross-purposes, searching for the last sanctuary at the end of the dead world...
A beautiful dystopia written by Hikaru Sakurai of the "Steampunk" series.

(Source: Seikaisha, translated)