Cha Yeon-woo learns that the twin brother who vanished years ago is dead, and is left with a pocket watch hiding the brother's diary. Its pages record a climb through the Tower of the Sun God, where dimensions converge, and the betrayal that killed him partway up. Armed with that record, Yeon-woo enters the Tower himself under the call sign Cain, using his brother's notes on its floors and traps to climb fast and hunt down the ones responsible. This manhwa adapts Sadoyeon's web novel.