The screenwriter Ran Choi was inspired by the Incheon Elementary School Murder Case that occurred in 2017, in which a 17-year-old girl murdered an 8-year-old girl. When she was imprisoned and asked what was the hardest thing for her now, the defendant answered, "The weather is nice, but not being able to go see the cherry blossoms is the hardest thing." Seeing that the murderer felt no remorse or guilt, Ran developed the drama against this backdrop, as she wanted to see 'psychopath murderers feel the pain, reflect on, and atone for their actions. Even if that's an impossible fantasy that they will have the same feelings as us and truly understand their sins and suffer. That would be the best punishment and salvation for the psychopathic murderers.'
The story of this series is based on concept of the "Psychopathic Gene". Psychopaths have the same brain as ordinary human beings, but without a mirror neuron. They do not feel the pain of others at all. Neither can they perceive other feelings such as guilt, sympathy, compassion, or regret. The screenwriter planned the drama in this backdrop.