Story about Houkiboshi's past.

Due to Ouka's rampage, the battlefield is dominated by mechanical dolls. Nameless Imperial Army soldier secretly infiltrates into enemy ranks for a certain purpose. In destroyed urban area with no survivors he meets a support doll Houkiboshi who miraculously escaped the rampage.
The two of them join hands and try to escape from this hell, but will they be able to?

[Translated from official site]