The war between the Terrans and the Vers Empire of Mars has ended, allowing humanity to blissfully enjoy their lives in a time of peace. Nineteen months later, however, the Vers princess makes a shocking public declaration: the Terrans are a foolish race that covets resources, destroys nature, and are devoted to the pursuit of pleasure. And so, to protect their precious Earth, she calls upon her knights to take up arms, and the raging battle between the two civilizations reignites. Slaine Troyard has found a place among the Martians, giving Earth a short respite from the war against the Vers Empire. However, a peaceful resolution seems inconceivable. The various people who fought desperately for survival in the past now find themselves in the midst of yet another bloody and chaotic conflict, one that will forever alter the fate of humankind.

During the late 19th century, Great Britain has become the greatest empire the world has ever known. Hidden within its success, the nation's rigid economic hierarchy dictates the value of one's life solely on status and wealth. To no surprise, the system favors the aristocracy at the top and renders it impossible for the working class to ascend the ranks. William James Moriarty, the second son of the Moriarty household, lives as a regular noble while also being a consultant for the common folk to give them a hand and solve their problems. However, deep inside him lies a desire to destroy the current structure that dominates British society and those who benefit from it. Alongside his brothers Albert and Louis, William will do anything it takes to change the filthy world he lives in—even if blood must be spilled.

In the backwater town of Bellforest lives a 14-year-old boy named Renton Thurston. He desires to leave his home behind and join the mercenary group known as Gekkostate, hoping to find some adventure to brighten up his mundane life. However, stuck between his grandfather's insistence to become a mechanic like him and the pressure of his deceased father's legacy, the only excitement Renton finds is in his pastime of riding the Trapar wave particles that are dispersed throughout the air, an activity akin to surfing. Everything changes when an unknown object crashes through Renton's garage, discovered to be a Light Finding Operation—a robot capable of riding the Trapar waves—specifically known as the Nirvash typeZERO. Its pilot is a young girl named Eureka, a member of the Gekkostate, who requests a tune-up for the Nirvash. Their meeting sparks the beginning of Renton's involvement with the Gekkostate as he takes off alongside Eureka as the co-pilot of the Nirvash.

Knowing that he is risking his life, Kei Kurono makes the uncharacteristic decision to jump onto train tracks to save a homeless man from death, only to perish in the process. But when he comes to, Kei finds himself in a room with several other recently deceased people, as well as a large, mysterious black ball. While the people in the room are trying to make sense of their situation, the ball suddenly opens, revealing a cache of weapons and strange black suits. The ball then instructs everyone that they have to hunt down an alien and teleports them to an unknown location. With very little information to work off of, Kei teams up with his childhood friend Masaru Katou and an unfamiliar woman, and the trio explore their new surroundings. It quickly becomes apparent, however, that they have stumbled into a dark and dangerous world where anything could happen to them.