Sung Jin-Ah is Jin-Woo's younger sister. She is a hard-working girl who usually tops her exams and has a close relationship with her brother since they are the only siblings in their family.

As she grew with only Jin-Woo next to her with her father got stranded in a gate and her mother ending up in coma due to Eternal Sleep, Jin-Ah was always on the edge whenever Jin-Woo is in the hospital and wanted him to stop being a hunter.

(Source: Solo Leveling Wiki, edited)