The competition comes down to two contestants: Gi-hun, and his childhood best friend Cho Sang-woo (Park Hae-soo). The final competition starts off with a coin flip, which is a symbolic representation of who these men are.
Gi-hun is the guy who tried to do everything right in life. He worked hard, played by the rules, believed in the system, and still ended up nearly destitute. San-woo, on the other hand, is the guy who took shortcuts to get ahead. Before the games, he was a wanted criminal who embezzled from his clients. Just like the coin flip that starts the game, all their choices were illusory, because both men wound up in the same place. They're just two sides of the same coin.
As the game plays out, Gi-hun defeats San-woo, but he also comes to see how rigged the game really is. He refuses to kill his former pal, and by offering mercy, he rebels against the game. But this is a futile gesture, because San-woo takes his own life in order to hand the win to Gi-hun.
Gi-hun "wins," but by this point he's already lost everything that matters. The show picks up one year after Gi-hun's "victory." His life isn't much different. Yes, he has the money. But while he was away competing, his mother died, and his ex-wife took his daughter to Los Angeles. And as a result of everything that has happened, Gi-hun has all but given up on life.
