Baek Yisoo is a young man in his early thirties who has a fit physique, opting for a tall, lean and muscular build. He has short black hair and blue eyes. 

He is calm, calculating, strategic, observative, careful, intelligent and inexpressive. Yisoo has an older brother (twin) who has an opposite nature to him.

Yisoo is a former team leader, northern infiltration unit, HID Special Operations Group, Republic of Korea National Military. Now he works with his older brother in the Gangster world.