A metropolis composed of innumerable clusters of residential buildings. Its streets and buildings are well maintained, and it contains all the public facilities and amenities needed for its residents to live in peace and comfort. The lights in the giant ceiling above the complex simulate day and night, and shelters are built into the ground to protect citizens from danger. Those peaceful days came to an end when the strange monsters attacked...
A peculiar school located outside of the Tokyo Residential Complex. It is humanity's last line of defense against certain destruction. The Special Defense Unit has been tasked with protecting the academy from the monsters attacking it for the next 100 days.
A team of remarkable young people charged with protecting Last Defense Academy, and by extension, the future of humanity. No matter what hardships the unit might suffer, they cannot be allowed to fail in their mission. To do so would spell certain doom for all mankind.
Strange creatures fixated on getting inside Last Defense Academy. Their ultimate aim is to acquire hidden somewhere in the school. If the Special Defense Unit cannot stop them, all of humanity will perish.
Powerful warriors that rule over the regular School Invaders. They are immune to conventional weaponry and can only be damaged with hemoanima. In addition to their formidable fighting prowess, each commander also possesses unique abilities.
A mysterious form of energy capable of gifting its wielder with powers so great that they border on supernatural. It is the only known force capable of harming the invaders. When activated, it solidifies into Class Armor and Class Weapons. The form these take is unique to each member of the Special Defense Unit. It is also what allows Takumi and the others to use their Specialist Skills.
Full name: Hematomorphic Infusion Blade. Widely regarded to be the pinnacle of human achievement and ingenuity, at least according to Sirei. When stabbed with one of these blades, a member of the Special Defense Unit has their blood replaced with hemoanima, allowing them to use special powers.
Otherworldly flames that never go out. A unique feature of Last Defense Academy, they surround the school up to a radius of 1 kilometer. They will incinerate any living matter they touch, making them an ideal defense against the invaders.