The heroine is an underground consultant who specializes in helping people plan "perfect revenge". One day, she received a mysterious big order: her employer paid a lot of money and asked her to plan a "perfect murder" against herself and make a specific person become the "perfect murderer." As the heroine investigates step by step, she discovers that her employer is actually her best friend who disappeared many years ago, and the designated "murderer" is the real culprit who forced her best friend's mother to death.
Reversal design: The heroine thought she was avenging her best friend, but in the last 10% of the plot it was revealed that her best friend had actually turned dark. She planned the murder to make the heroine a scapegoat. In fact, the heroine has seen through all this a long time ago. She followed the trend, took advantage of the situation, and counterattacked at the last moment, so that the real villain got the punishment he deserved.
Intention: A seemingly perfect "revenge" plan is actually a carefully designed "killing" game.