Yeonwoo's brother vanished years ago, leaving him devastated upon learning of his death. While coping with this loss, he receives a pocket watch and discovers that his brother's death involved more than meets the eye: he was betrayed while competing in the Tower of the Sun God. Now, Yeonwoo must utilize the knowledge his brother left behind. Can Yeonwoo (call sign: Cain) navigate that world, acquire sufficient power and experience to reach the tower's summit, and defeat his brother's enemies along with anyone else who stands in his way?