1st Floor is a man with a limp who is pushed to the brink of his sanity during the game. Bae Seong-woo plays the character.
1st floor picks the number one card before realizing that he was picking what floor he stayed in.
He was thankful for getting the lowermost room since he has a constant limp. That turns into disappointment once he finds out that he has the smallest room and earns the least.
When they figure out that going up and down the stairs adds time, 1st floor is one of the weak links, and Sixth floor bullies him for it.
Second and Third floor take turns covering for him and he feels guilty for making them work harder.
His room is the spot where everyone gathers to eat the extra food, but that doesn’t become feasible after his suggestion.
To cover up for his inability to contribute as much, he offers to stash everyone’s waste products.
They start sending it down to his room and he stacks it up until it gets quite unbearable to sit in there.
A clear goal
During their discussions, 1st floor said that he would need to earn one billion. They decide that that would be their cut-off to end the game.
When they realize that it is entertainment and not running, 1st floor reveals his talents as a clown in the talent show.
He earns the second most time out of everyone and then requests not to be the waste holder anymore.
The responsibility shifts to Bae Jin-su, but more trouble arrives when they start playing the game ‘King’.
He figures out that it is rigged in favor of the upper floors and they tell Seventh floor about it, but that only gives the upper floors the impetus to assert full control.
1st floor is the spark of hope after much torture as he comes up with a plan to revolt. He tells Second and Third floor to use the lift and sneak into his room.
With Seventh floor’s help, they take back control of the place. They decide to let the timer run out and Second floor offers to give 1st floor the balance he needs to reach one billion.
Then the clock has time added on and upon investigation, they discover the Sixth floor and Fourth floor were tortured.
There is another power shift and Sixth floor interrogates the others to find out who pulled out his toenails and did unspeakable things to him.
Jin-su suggests buying the camera footage, which reveals 1st floor as the culprit just as he confesses.
He insisted on making the one billion inside, and got revenge on Sixth floor for bullying him in the process.
Eighth floor takes control of the situation and has everyone else restrained and tortured until 1st floor says that he needs the billion to change rooms.
When he first entered, he asked if he could change rooms and the cost shown to him was one billion.
All for his daughter
1st Floor’s real name was No Sang-guk and he worked as a clown at the circus. His daughter suffered from a rare disease but he couldn’t afford her treatment.
He tried to commit suicide so that his family would benefit from his life insurance policy, but he entered the game show instead.
He settled on changing rooms so that he could go back to his daughter with his head held high, but things took a turn for the worst.
1st floor said that he wanted to use his own prize money to change rooms, but it turned out to be just the price of instructions and the real costs of changing rooms.
Losing his money for nothing, he has a psychotic break and restrains everyone before making them watch his routine which includes a tightrope act.
He bounces on the rope and reaches the ceiling which ultimately leads to his demise. He falls and is engulfed in flames from the broken projector.
He says that he wanted to crawl out of the hole and everything he did was for his family.
Jin-su tracks down his family months later and finds out that Seventh floor handed them a ton of money and told them that 1st floor was on a job abroad.
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