Yeonwoo, who had forgotten his twin brother who disappeared 5 years ago, receives his brother's pocket watch. Inside, he finds a diary that reads, 'By the time you find this diary, I will no longer be in this world.' The diary reveals a world where multiple dimensions and universes intersect, centered around the Tower of the Sun God, the Obelisk. Yeonwoo's brother had climbed the tower but was betrayed and killed. Armed with his brother's diary, Yeonwoo begins his own ascent of the tower to find out what happened and uncover the truth behind his brother's death. This is Yeonwoo's journey to find his lost brother.