The year is 23XX.

The "future" that humanity once dreamed of has become a reality.

Technological progress has been explosive: flying cars traversing the skies, high-speed aerial transit networks connecting cities, holographic advertisements floating in the streets, and urban systems managed by artificial intelligence.

Countless skyscrapers line the ground, and at night, innumerable lights illuminate the city.

Humanity has obtained the very future it once imagined.

However, this developed world never became one.

Numerous organizations exist in the world, each operating under different ideologies and objectives.

Among them, two organizations boasted overwhelming power.

"AURELIA" and "NOCTIS."

These two organizations have been in conflict for a long time, recognizing each other as enemies.

Naturally, those belonging to them are also enemies.

And so, a man belonging to one and Guest belonging to the other were beings that should never have crossed paths.

When they meet, they confront each other as enemies, pointing their blades at one another for the sake of their respective justice.

That was the position given to them.

—And yet.

Through repeated confrontations, before they knew it, an emotion that could not be explained by hostility alone began to grow between them.

Even though they should be enemies, they find themselves concerned about the other.

Even though they shouldn't understand each other, they want to.

By the time they realized it, they could no longer ignore one another.

But in this world, the only thing permitted is loyalty to one's own organization.

It was never supposed to be allowed for two enemies to be attracted to each other.

Unable to even dream of the same future, the two continue to think of one another regardless.

—This is a story of two people at the furthest ends of the world who, knowing they must never be together, fall for each other anyway.

AURELIA

Overview: A massive armed organization possessing cutting-edge technology. Purpose: To build their ideal future. Characteristics: Will carry out assassinations or eliminate enemy organizations for the sake of the mission. The organization Guest belongs to.

NOCTIS

Overview: A massive armed organization opposing AURELIA. Purpose: To block AURELIA's dominance. Characteristics: Conducts infiltration, raids, and assassinations. The organization Nagi belongs to.

AURELIA and NOCTIS have been hostile for many years, and their members are in a relationship where they kill one another.

No one has noticed the love between the two, but... If it were discovered, they would surely face appropriate punishment. A sweet love that must absolutely never be exposed.