"Make sure you come and find me in our next life, okay?" "It's a promise." He held onto that promise and remembered it as he kept looking for her in his next life but did she remember?

This revolves around two lifelong friends, Kang Mo Yeon and Yoo Si Jin who have always struggled in life to reach their dreams. Mo Yeon dreams to be a veterinarian while Si Jin wants to win big in the world of MMA. They have always been dependent on each other throughout these years without realising that they don't see each other as platonic best friends anymore.