The story is centered around a small group of guerilla freedom fighters on a colonial planet named Deployer, who are known as the "Deployer 7", or "Sun Fang" team. In an unexpected coup, the elected Governor of Deployer becomes dictator and rules Deployer under martial law with the support of Earth's Federation. Fighting for independence from Earth's Federation influence, the freedom fighters begin a rebellion against the Federation's Combat Armors using a Combat Armor of their own: the Dougram.

Taking place after the events of Heaven and Earth and before Exodius, Behind the Line depicts the moments of boys and girls after Soushi Minashiro returned home.

Episode 13 included with the Blu-ray/DVD release.

Two hundred years ago, on the Battlefield of the Blue River, the last remaining army of the Empire of Light collapsed in the midst of demonic outcries. As the last Field Marshal and Emperor fell, the chaotic world of the Western River no longer had a common ruler. Factions were formed and endless conflicts ensued, military might became the only currency of survival, and the dream to reunite the lands became the sole goal of many rulers in the generations that came after. In the south-eastern part of the land, a powerful faction with over two hundred years of history – House Zichuan – fought off the Demons to the east, defended against the House Liufeng to the west, and contained the House Lin to the south. In order to accomplish their great ambitions and extend the bloodline of their family, countless heroes of Zichuan gave their lives in order to make this magnificent hymn come to life. This is a story about this legendary family and a hundred years of their blood and tears.