Born into an ordinary family, the plump girl Kim Yeon-ju had always been an inconspicuous presence at school, accustomed to living quietly without ambition. However, she harbored a secret romance she couldn't confide in anyone: a secret relationship with Eom Seong-hyeon, known among girls as the 'ideal type,' which had lasted for three years. But this sweet, dreamlike romance shattered when she overheard Eom Seong-hyeon mockingly call her 'just a fat girl I casually dated' in front of his friends. From that day on, Kim Yeon-ju disappeared without a trace. Seven years later, she returns, completely transformed, living under a new name, 'Yoon Ye-jeong.' Now a cardiac surgeon, Eom Seong-hyeon reappears before her, along with the daughter she raised on her own.