S1, E6: After Ba Tang collapses during the exam, Yi Soo carries her on his back and runs. While doing so, Yi Soo remembers how cold his mom\u2019s body had steadily become. The traumatic memory of how Yi Soo had to bear the fear of death as a young boy rushes back to him. Yi Soo only just manages to pass the exams but feels uneasy in the back of his mind.