Stupidity: When Sook-Hee and Hideko are leaving the mansion to meet up with Fujiwara, they run past a rope and noose tied to a tree. Later on, it's revealed that this rope was tied to the tree because Hideko attempted to hang herself. Despite abandoning the suicide attempt and coming up with a new plan to scam Fujiwara, they leave the rope tied to the tree, even though this could potentially expose the scam to someone at the mansion. (00:53:32 - 01:47:15)
Stupidity: Sook-Hee and Hideko manage to escape Japan with the money by disguising Hideko as a man named Go Pan-dol, including forging a passport with Hideko in the disguise, then getting onto a ship headed for Shanghai. Once on the ship, Sook-Hee removes the moustache Hideko was wearing as part of the disguise and then throws it into the ocean. Even if they have escaped all trace of Kouzuki and plan on creating new identities once they have settled in Shanghai, they still need to prove that she is the man in the forged passport that she is posing as if they are to enter the country when they arrive in it. Getting rid of the moustache could potentially ruin the disguise and give away her real gender. Surely it would be a smarter idea to get rid of the moustache once in Shanghai. (02:14:40)
Stupidity: When Sook-Hee walks into Hideko's bedroom before the two of them have sex, she slides the door open when going into the room and never closes it behind her. Once the two of them are in bed together and when they have sex, the door is left the way it is and never closed. Considering a sexual relationship between the two would have been completely forbidden, and, if they were caught, would likely ruin the plot to steal the inheritance money, it seems very foolish of them to ignore the open door, especially taking into account there are other people inside the mansion who could walk by at any moment. (00:41:30)
