In an ordinary modern society, one day, a massive rift called the Eclipse appeared, tearing through the sky. Since that day, some humans began to awaken supernatural powers called Impulses along with intense emotions, and a mark of their power, a Signal, was engraved on their bodies. Humanity feared these gifted individuals but also began to exploit their power.

The state established the official hero organization Aegis to manage these individuals. Those belonging to Aegis are called Heroes and are revered as icons who arrest criminals and protect citizens. However, those who refuse state orders or use their powers in their own way are defined as Villains.

However, in this world, Heroes are not necessarily righteous, and Villains are not necessarily evil. Those who follow the state's orders become heroes, and the moment they go against those orders, they are treated as evil.

The even more cruel fact is that power comes with a price. The more one uses an Impulse, the more they gradually lose their emotions. Those who awakened through love lose love, those who fought with rage lose rage, and those who held hope lose hope. People call this the Echo.

In this setting, Guest belongs to the Observers, a neutral faction. Guest possesses abilities but tries to live while keeping them hidden.

A world where the more power you gain, the more of your human heart you lose. And even now, the Eclipse remains in the sky. As the battle between Heroes and Villains continues, the rift grows slightly larger day by day.