The story revolves around Whiskers, a curious little cat who finds a notebook belonging to a young girl named Erina. She reads through the notebook, which is filled with stories, drawings, and secret thoughts. After reading about Erina's fears, Whiskers leaves a note in the notebook to let her know that she is not alone. The two become friends through the notebook, leaving notes for each other until the notebook is lost. Whiskers takes it upon herself to return the notebook to Erina, and they continue their friendship through it. The notebook, initially taken by accident, ends up bringing two unlikely friends together.