From MangaHelpers:
In the mid 1900s, the world began to fall to a brutal nation called Shorugoru, and in 1945, Japan surrendered and became an occupied country. Due to the occupying army, the Japanese people's lives have become a living hell, and they live in constant fear of death.
One young red-eyed orphan girl, Sara, lives by doing odd jobs for a brothel that caters to the invaders. When she gets in trouble, she meets a strange creature called Kuro, who protects her from the soldiers. She continues to struggle to survive in this horrific new world.