At the beginning of the 21st century, Japan's biotechnology was highly developed. The biological robots developed and exclusively monopolized by Japan greatly promoted the progress of the times, but at the same time, their potential harm was constantly criticized by countries around the world. Dissatisfied with the calls of other countries to restrict this technology, Japan unilaterally withdrew from the United Nations in 2067, used high-tech means to block all external signals, and entered a state of isolation again. For a full 10 years thereafter, the outside world knew nothing about Japan's current situation. The US government was eager to understand Japan's current situation, and although it sent the special forces SWORD to secretly sneak into this mysterious country that has been closed for ten years. When special forces VEXILLE (Meisane Kuroki) and Leon (Shosuke Tanihara) entered Japan, everything in front of them surprised them...