Sanu

In public, he has a "happy, energetic" face and is shown to smile frequently, even when making eye contact with strangers in social settings. During his time at university, he came across as an extrovert with a large circle of friends. According to Bum, he attracted many people with his "sensitive, considerate, gentle aura". However, these traits mask his true psychopathic, cruel, and sadistic traits. Sang-woo is actually a cruel and ruthless man who kidnaps, abuses, tortures, rapes, and kills people, showing absolutely no mercy to his victims, and is completely fine with beating and torturing his victims, even if they are women, and/or begging for their lives, showing no remorse for any of his actions. A sadistic sociopath who takes pleasure in the pain of others, he is extremely narcissistic and looks down on everyone, pretending to care about others only to strike them with genuine hostility when he feels like it. His emotions when confronted with his victims alternate unpredictably between false mercy and violent hostility. When talking to acquaintances, he teases them in a lighthearted tone and does not hesitate to get closer to strangers while doing so. He uses derogatory, harsh language towards his victims, insulting them. He tortures his victims slowly but at a certain pace, preferring to also manipulate them, coddling them with cutesy words and behavior before returning to his cruelty. He prefers female victims, although he has no qualms about men, despite not having killed a single person since the death of his father in high school. He is also a rapist and necrophiliac. Despite stating that he doesn't like it when guys scream, he rapes Bum three times throughout the story. He displays his necrophiliac tendencies by stripping all of his victims naked and defiling their corpses after killing them, groping the corpse of the CEO's deceased daughter after killing her. Just like Uncle Yoon-beom, Sang-gu uses Bum as a substitute for the woman he is obsessed with, which leads to him verbally abusing Bum and using him for his own pleasure. He also thinks that Bum is to blame for being raped regularly by his uncle, and he always blames Bum when he tries to defend himself from Sang-gu's abuse towards him.