Kang Sae-byeok is very stoic and usually aloof. She is also level-headed and can stay calm in dire situations. In short, She is very quiet and calm, never panicking even in stressful moments. She rarely expresses her emotions to anyone excluding her little brother and her middle sibling. 

Sae-byeok and her siblings is living through poverty before in North Korea, until they escaped and transported to South korea in Incheon, she's trying to look for part-time jobs to take care of her relatives.