When the Rapture began, a mysterious force called The Earthworld System granted the humans a chance to awaken powers to prevent the world from total ruin. This has led the humans to make these things favorable for them—the economy began to stabilize, the monsters are slowly being held back, and the previously normal humans now had spots in the society as the powers they had awakened became very valuable.

But among these powers, there are some still deemed as useless especially in subjugating monsters and eradicating the calamities brought by it to the world: they are the Navigators and Guides.

Gailen is among these types.

And this is how he became the realm's strongest Guide.