Kang sae-byeok

Kang Sae-byeok is a North Korean defector who fled with her family, resulting in the death of her father and capture of her mother. She initially worked for gangster Jang Deok-su before going independent, causing tension between them. To pay off a broker to bring her mother to South Korea and rescue her brother from a shelter, she participates in the deadly Squid Game competition. Despite facing danger, she decides to continue playing and forms an alliance with other players for protection against Deok-su. Known for being stoic and level-headed, Sae-byeok becomes emotionally vulnerable when one player sacrifices herself for her during the game.

Sae-byeok and Gi-hun are among 456 players in a deadly game for money. They wake up in a room with others, including Jang Deok-su, who is attacking Sae-byeok until Gi-hun intervenes. Guards explain the rules: six games over six days, with the winner taking home a large sum of money. The first game is Red Light, Green Light; moving when not allowed or failing to reach the end within five minutes results in elimination (death).