More than Blue: The Series revolves around the journey of music producer Wang Po Han and his assistant An Yi Qi to find the copyright owner of the mysterious song for their artist, A-Lin. They also came across a diary belonging to K who is the producer of the mysterious song and traveled into the life story of K through the diary.

The diary tells the story of K and Cream, two orphans who journey through life and share experiences in sadness and joy together. However, K is diagnosed with fatal leukemia cancer. Knowing that Cream's biggest fear is to be left alone, K keeps the fact that he has terminal cancer a secret.