In a world where everything has fallen apart, the only remaining apartment complex has become a marketplace where everything is traded. One day, a mysterious girl named "Hee-ro" enters the space, and cracks begin to form.

Before the world collapsed, Hee-ro's reunion with her friend Se-jeong, her only hope, was fleeting. With something to protect once again, Hee-ro remains in the Imperial Palace Market, plotting to overthrow Park Sang-yong, the ruler of the 9th floor.

Hee-ro joins the Taejin group, a group that has been a key player in the market. Taking advantage of Taejin's precarious situation and his shortcomings, she begins to orchestrate a new deal.

Hee-ro's operation, which seemed to go smoothly, runs into Tae-jin's deeper loyalty to Park Sang-yong than expected. To make matters worse, the market's core resource, groundwater, is blocked, creating a new crisis, and Heero sees another opportunity in it.

The new plan is put in jeopardy again by Taejin's rival and the manager of the 8th floor, Cheolmin. In order to survive, Heero takes a step toward a more dangerous choice.

All of Heero's plans are revealed. In the confusion of not knowing whether his faith was used or whether he was taken advantage of, Heero comes face to face with the truth that he himself had been missing.

Dawn dawns, and Hee-ro, who has climbed up with only eyes on the 9th floor, finally reaches the hidden truth on the 8th floor. After understanding Se-jeong, she reflects on the relationships around her and embarks on a final mission to save Se-hee and everyone else.