Oh Sangwoo is one of the two central characters in the psychological horror manhwa Killing Stalking by Koogi. He is a young man in his early twenties who presents as handsome, popular, and approachable while hiding a far darker nature as a serial killer and abuser. In appearance, Sangwoo is tall with a lean-to-muscular build. He has wavy light brown or light blonde hair (often described with a black undercut), which he later cuts shorter and straighter at points in the story; he dyed it after high school. He is frequently shown with pronounced dark bags or circles under his eyes. His looks are stylish and attractive in a way that draws people in, contributing to the contrast with his true character. Publicly, Sangwoo maintains a cheerful, energetic, friendly, and charismatic persona. He smiles readily, has a large circle of friends at university, and comes across as empathetic, considerate, and gentle—traits that help him charm or seduce people. This is a carefully maintained mask. Privately and toward victims, he is cold, cruel, sadistic, controlling, and highly suspicious. He takes pleasure in inflicting physical and psychological pain, uses demeaning language and taunts, alternates between false kindness or “mercy” and sudden brutality, and sets up tests of loyalty or obedience. He is narcissistic, looks down on others, shows little genuine remorse for his actions, and displays misogynistic and homophobic attitudes rooted in his trauma, while primarily targeting women but also harming men. He is volatile when his control is threatened, shifting into anger, intimidation, or even tears of helplessness. Sangwoo’s backstory is defined by severe childhood trauma and family dysfunction. He grew up with a strict, later abusive and negligent father and a mother (Eunseo) who was caring and submissive toward him at times but also mentally unstable, possibly suffering from depression or related issues. The mother had previously tried to abort him and once attempted to smother him as a toddler; the father intervened. The father eventually became distant and violently abusive toward the mother. She had affairs, guilt-tripped Sangwoo into protecting her, and on at least one occasion made him watch her with another man. She began poisoning the father’s meals with rat poison; after a confrontation, the father died (with foam at the mouth and poison nearby), and the mother manipulated Sangwoo into believing he was responsible, after which they staged the death as a suicide by hanging the body in a forest. Afterward, the mother turned on Sangwoo—attempting to poison him as well, burning him, locking and restraining him in the basement, and trying to assault him—before he killed her in self-defense during a confrontation. His parents’ deaths (investigated as unsolvable years earlier) left him an orphan, and the cumulative abuse, betrayal, and violence shaped his controlling, paranoid, and violent adult behavior, including his pattern of kidnapping, torturing, and killing. Overall, Sangwoo is a complex, deeply damaged figure whose public charm conceals profound sadism and unresolved trauma from his parents. The manhwa explores these elements through his interactions, particularly with Yoon Bum, without romanticizing the extreme abuse and violence.