Barrier Cracker

is a Japanese light novel series written by Kyonosuke Seki, with illustrations by KeG. The series began publication on August 8, 2015 by ASCII Media Works under their Dengeki Bunko publishing imprint.

The series won the Dengeki Bunko Magazine Prize in the 21st Dengeki Novel Prize.

Synopsis
A rugged mercenary Kyle and an innocent girl Nine. Under the polluted sky, the two meet.

In a pollutant-covered world, mercenary Kyle met a girl floating in culture deep inside the ruins. A young mechanical girl who has no name and can't understand words well.

"You don't have a name. Do you understand?"

"Nine? I, Nine!"

Nine with an unknown fighting ability and Kyle who has been certified as her master for some reason. They decide to travel the world abandoned by humankind in search of Heaven's Gate, which is said to lead to paradise.

Sometimes like a parent and child, and sometimes like a brother and sister. And sometimes like a lover. The relationship between the two changes during the journey. And what is the reason for Nine's tears that flows after finding hope for the future? This is a love story tied to the end of the world.