Kang saebyeok - Urban Dictionary: Kang Sae

She was a North Korean defector, and fled the country with her parents and younger brother, leading to her father's death and her mother getting caught.

She also tells Ji-yeong that a plague in her village had killed her grandfather, grandmother, and older brother, and so she and her younger brother were the only ones who successfully crossed the border to the South Korea.

The one who should have a reason to get back out there.

She helped him pass the fifth game and even prevented him from killing Sang-woo, appealing to his sense of virtue.