Sung Jinah, younger sister of Sung Jinwoo, endured a childhood shaped by familial hardship. Her father vanished in a dungeon ten years prior to her birth, depriving the family of its main provider. Her mother later fell into an Eternal Slumber coma due to mana exposure from Magic Beasts, compelling Jinwoo to sustain them as a hunter. Amid financial strain, Jinah excelled academically in high school while relying entirely on her brother for support.

Physically, she has brown hair worn in a ponytail with bangs and stands shorter than Jinwoo. Her standard attire included a school uniform of blue jacket, white collared shirt, and red tie. At home, she occasionally used hair accessories.

Jinah displayed a positive, diligent, and caring nature, sharing a close bond with Jinwoo. Fearing for his safety after repeated hospitalizations, she urged him to quit hunting and once threatened to abandon her studies if he suffered further injuries. Driven to cure her mother, she aspired to medical school. She cherished ordinary routines like shared meals, arcade visits during middle school, studying, and sleep, yet recoiled at Jinwoo’s injuries or hunter-related dangers.

Her life shifted when targeted by the orc warlord Guroktaru, an ordeal causing lasting trauma that muted her cheerfulness and amplified anxiety over Jinwoo’s safety. This deepened Jinwoo’s attentiveness to her emotional state, strengthening their mutual care. She eventually married Yoo Jinho, Jinwoo’s associate, embracing a civilian life detached from hunting.

Jinah remained an ordinary human without hunter abilities, with Jinwoo forbidding any involvement in the profession to prioritize her safety. She named his guild "Ahjin" by reversing syllables of her name. Throughout her narrative role, she embodies Jinwoo’s motivation for power, symbolizes the civilian-hunter dichotomy, and serves as his unwavering emotional anchor.