After enduring twelve years of relentless nightmares that robbed him of proper sleep, Ujin Kim eventually dies—only to awaken inside the very world that haunted his dreams.

Now surrounded by demons of all shapes and horrors, he quickly realizes he has been reincarnated into the body of a mercenary. With no other choice, he sets out in search of civilization while trying to make sense of this unfamiliar reality.

He soon discovers a world filled with magic, a Church actively waging war against demons, and countless suspicious individuals operating in the shadows. Yet despite the chaos and danger, there is one unexpected comfort—at least, for the first time in years, he can finally sleep peacefully.