Seong Su Ji is the main character of the drama "Pyramid Game". The main character is rational and intelligent, smart and capable. She has a strong mental strength and is very strong, so her evaluation is good.
Sometimes, there were opinions that Su Ji was difficult to empathize with because she's too rational for an ordinary high school student, but there were many cases where she was greatly influenced by her emotions as well.
Su Ji also shows tremendous power. As soon as she became a C-grade, She could quickly adapt and get closer to her classmates, and she approached those who bullied her without hesitation. Su Ji's mindset is quite similar to that of Baek Ha Rin. However, Baek Ha Rin has the opposite purpose of Sung Su Ji's regarding of the pyramid game.
(Source: Korean = NamuWiki || Translation = MyDramaList)