“If we’re still single at thirty, let’s marry each other!” It was a childish promise she made jokingly with her childhood friend back in middle school. Time passes, and the year she turns thirty finally arrives. Yeon-hwa, who had been planning to marry the boyfriend she’d been dating since college, is suddenly shocked by his declaration of breaking off their engagement. While walking in a daze, she gets hit by a car. When she wakes up, ten years of her memories have disappeared and her childhood friend is acting as her guardian. “A guardian? You’re my guardian?!” “Did we… actually get married?!”
