When he came to after losing consciousness, he suddenly found himself in the far future; on a different star system. After being guided by an enigmatic cat and a young girl, what Mozuya Kou ended up encountering was the abandoned mass-production machine "TSW-R1 Lanius". Its only weapon was a gigantic sword.

This battlefield, called the Nemesis Warfront, was a place where countless weapons of murder and the people and organizations that operate them continue to engage each other in brutal battles. Kou is given the [Building Engineer] qualification by a young girl who manages the planet Ashia, and was tasked to design and develop various weapons.

He was to cooperate with people and companies who, like himself, were also transported to Planet Ashia from 21st century Earth in developing and sortieing armaments such as human-shaped mobile weapons (giant mechs), armed rail-cars, drill tanks, vertical take-off and landing heavy assault aircraft and the like.

Thus begins the tale about weapons development taking place on the far flung Nemesis Star System.