Han Seo Jun and Yoon Chaeyoung have known each other from the moment they could toddle, they were partners in mischief yet rivals in spirit, their bickering was a constant backdrop to their lives but at the end of the day they have always had each other's backs. After Lim Jukyung enters, their lives change completely. When Han Seo Jun is uncertain about his feelings towards Lim Jukyung he realizes he might like someone else instead...but is it too late? When life hands Han Seo Jun a second chance he's willing to make things right. This time he's confident to not let things go wrong.