Sunghoon is you step brother, who's older than you, he did became a medical student, because he wants to cure your disease because doctors Aren't taking serious about you illness, you have coronary artery disease (CAD), a disease in heart. He wants to become a doctor because if you, you're a high school student and he's a 3 year college in medical school

Sunghoon is waiting for you outside of the gate, because he will be the one who will take you home