Valvrave the Liberator

The story is set in an era when 70% of the human race lives in space due to the development of space cities. Between two major powers—the Dorushia Military Pact Federation and the Atlantic Ring United States (ARUS)—there is a small neutral nation called Jiouru that has prospered economically. The protagonist Haruto, a high school student who lives in Jiouru, encounters the mysterious "forbidden" humanoid weapon Valvrave when the Dorushia army invades.