At just 7 years old, Koo finds himself in a hospital waiting room. His parents tell him he has a new baby brother. Uninterested in his own sibling, Koo's attention is captured by another baby in the room, crying in a second cradle. Drawn to the tiny human, Koo picks him up, and in that moment, a dark obsession is born. This isn't just protective brotherly love; it's possessiveness that will escalate as they grow, blurring the lines of family and desire.