When Li Yue traveled to the Demon King's castle, he was not a cool vampire or a mysterious magician, but a naked brain spirit? Fortunately, the brain spirit has the ability to perceive thoughts, move objects through the air, and have soul impact... at least it counts. It is a magical creature. Li Yue, who has unlocked the devil's illustrated book, will start from a brain spirit, collect strange monsters, transform his inner demons, summon gods and monsters from other worlds... wander through chaos and darkness, and climb to the top of the Demon King's City step by step.