Oh Jong is a single mother of three children, all from different fathers. She has a talent for coffee roasting, and her bright personality and desire to share happiness and stories through her coffee makes her a popular sight at Ji Suk's coffee shop. Choi Chang, a straightlaced and no-nonsense businessman, disagrees with Oh Jong's methods and believes that coffee-making is a mathematical science that uses exact measures. Despite their clash of personalities, Choi Chang finds himself opening up to Oh Jong's warmth, discovering a love as exciting and flavoured as the coffee she serves.