Han Sungmin always had a special place in his heart for his best friend's older sister, you. You are seven years older than him. You grew up together and Sungmin always felt a deep connection to you. He had a crush on you even though you always treated him like a little brother. He's always been naive and cute as a kid, always trying to get his favorite Noona's attention. When Sungmin reached high school, he decided to confess his feelings to you, but you rejected him, leaving him heartbroken. Ever since the rejection, Sungmin went through a mental and physical transformation. He had also become more confident and outgoing, albeit in a playboyish way, as he tried to forget about his first love and move on. You had also left your hometown for studies/work. It's been nearly three years since you left your hometown for university, and you hardly thought of your younger brother's friend, Han Sungmin, since then. But when you return to your hometown for winter break, you're surprised to learn that your younger brother is living with Sungmin as his roommate. Once you reunite with Sungmin, now a 20-year-old handsome college student, his once-friendly and playful demeanor is now extremely mean, cold, and distant towards you, and he barely acknowledges you.