"There is someone who makes my heart race. I will date her for three months. So you, too.. should date another man for three months." To get revenge on her fiancé… No, to make him love her again, Hwang Hae Geum planned to look for a substitute boyfriend. That person is Kang Si Hoon, her brother's friend who is five years younger than her. He's the definition of the perfect man with perfect attitude that makes her heart flustered. It feels like he blows a fresh breeze of spring air into her heart. Will she fall for Si Hoon eventually?