Oh Sangwoo is the primary antagonist of Killing Stalking. He was a classmate of  and was enlisted in the same military as him. He saved Bum in the past from sexual assault from his superiors, which caused Sangwoo to be the object of Bum's obsessive affections. Sangwoo is frequently seen in the company of female admirers. He adopts a "happy, energetic" face and is shown to be often smiling, even when making eye-contact with strangers in social surroundings. During his time in the university, he decided to be an extroverted person with a large circle of friends. According to Bum, he attracted many with his "empathetic, considerate, gentle aura" and ultimate sugoiness. These traits, however, mask his more psychopathic, sadistic characteristics. His emotions, when facing his victims, alternate unpredictably between mercy and violent hostility. When speaking to established acquaintances, he teases them in a light-hearted tone, and isn't above making better acquaintances with strangers by doing so. Around his victims, he utilizes demeaning, harsh expletives, berating them with slurs. He tortures his victims slowly, yet with a certain pace, selecting to also manipulative them with simpering words and conduct before returning to his brutality. He appears to favuor female victims, though not hesitant about males, either, despite having not murdered a man since his father's death in high school.
Oh Sangwoo is tall, with a muscular physique, possibly results from his training in the military. He has a spiky quiff with short sides hairstyle with his front hair is the colour of tan with short black sides. He has brown eyes with prominent bags beneath them.
Oh Sangwoo's personality can change depending on whether he is in public or alone with his captive(s). In public, he is seen as a friendly extrovert with a positive attitude. He is truly psychopathic and quick to change in temperament, alternating between mercy and extreme punishment when dealing with Yoon Bum, his captive.
|Main||Oh Sangwoo | Yoon Bum | Min Jieun|
|Police||Yang Seungbae | Officer Park | Junjae|
|Season 1||01 | 02 | 03 | 04 | 05 | 06 | 07 | 08 | 09 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19|
|Season 2||20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35|