In a world reduced to rubble, the last-standing apartment complex has become a cutthroat market where everything is for sale, trading in the only currency left: survival. The arrival of a mysterious girl named He-ro threatens to shatter the fragile order of this concrete jungle.

The reunion with Se-jung, once He-ro's entire world before the collapse, is tragically short-lived. Driven by a newfound purpose to protect what remains, He-ro stays behind at Hwang Gung Apartments to plot the downfall of the 9th-floor tyrant, PARK Sang-yong.

Now embedded within Tae-jin's crew, a pillar of the market's power, He-ro begins to see the cracks in his authority. By exploiting his precarious standing and his deep-seated insecurities, she starts to manipulate the market's trade, setting the stage for a much larger gamble.

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.