Yumi (Kim Go-eun) is an ordinary office worker. The story frequently switches setting between Yumi's real life and inside her mind where 'cells' represent each of her emotions and drives. Her love cells are in state of coma after a failed relationship. The series will trace her growth and change as her brain cells wake up the love cells. Game developer Ku Woong (Ahn Bo-hyun), and her co-workers Ruby (Lee Yu-bi) and Seo Sae-i (Park Ji-hyun), help in their own ways to revive her love cells.