Japan is under threat from mysterious extraterrestrial life forms. Two-thirds of the world's population has perished at the hands of these aliens. Their appearance is nothing like humans, and their physical capabilities are off the charts. A single one is a disaster-level threat. The moment you encounter one, you instinctively prepare for death. There is an organization that serves as humanity's last hope.

"Special Task Force Against Extraterrestrial Life: Aegis"

• Official Name: Special Task Force Against Extraterrestrial Life
• Alias: Aegis

Citizens call them "Humanity's Last Shield." Aegis is divided into districts such as Hokkaido, Tohoku, Kanto, Chubu, Kinki, Chugoku, Shikoku, and Kyushu, with multiple special task forces in each district. Members are recruited through volunteering, and only the most exceptional individuals can join.

Here, the extraterrestrial life forms are referred to as "Variants." The Kanto region has four units, each consisting of five members. There are four special task forces in Kanto.

Each unit consists of one captain and four members, totaling five people. They live together at the Aegis Kanto Headquarters.

All members use government-approved powered exoskeleton suits called "OVER" and special weaponry capable of damaging Variants. Special weapons are chosen based on the member's abilities or personal preference. The suit's helmet can be retracted with a single button. The mask is often retracted during conversation.

Even when using similar equipment, combat philosophies differ greatly between units.

Among them is the Kanto 4th Special Task Force: Nocturne. A unit with high skill, but viewed as somewhat unorthodox by other units.

■ 1st Special Task Force: Ark The most orthodox combat unit among the Kanto task forces. Responsible for frontal combat against giant individuals and high-risk individuals.

■ 2nd Special Task Force: Raven A unit specialized in reconnaissance, tracking, and sniping. It is said that by the time they discover a Variant, the battle is already over due to their long-range combat capabilities.

■ 3rd Special Task Force: Valkyrie A unit that prioritizes rescue, evacuation, and escort over combat. In addition to fighting Variants, they are responsible for rescuing civilians from collapsed cities.

■ 4th Special Task Force: Nocturne "If you can't win, create a situation where you can." The unit led by Guest. The most unique among the four units. They specialize in improvised tactics that combine the abilities of all five members.

Their decision-making during combat is exceptionally fast. They are the type to "create the optimal solution on the spot" rather than "act according to the plan." Furthermore, the 4th Unit has not suffered a single casualty in the past three years.

This is because they strictly adhere to a fighting style focused on "surviving no matter what."

...However, because of this, other units say, "Those guys depend on their comrades too much."

Why the Variants continue to kill humans and why they invaded remains a mystery.

Solving the mystery is also your job.