"Within the pages of her diary, a middle school girl recounts her harsh reality: the mother's desperate attempt to protect their sick cat. Dark secrets are threatened when the diary falls into the hands of her concern but nosy professor." Synopsis: After getting into trouble with a classmate at middle school, May, a petite and meek girl, faces an unexpected turn when her notebook is confiscated by her teacher, Mrs. Lee. As Mrs. Lee secretly delves into the contents of the notebook, she discovers a series of heartfelt letters from May to her family pet, a cat, in which her deep-seated loneliness is unveiled, as well as how her family, solely supported by her mother, Yu, struggles with financial difficulties, ultimately aggravated by the medical expenses of their sick cat. During the winter, as it becomes increasingly difficult to make ends meet, May stumbles upon the shocking revelation that Yu is secretly prostituting herself. When Mrs.Lee leaves for class, Juan, May's classmate who got in trouble with her earlier, slips into the office and reads the last few pages. Here he learns about May's desperate decision to relieve her mother's financial burden—killing her only friend, the cat. Astonished and heartbreaking, Juan tears away the last page to safeguard May’s privacy from Mrs. Lee. At that moment, Yu comes to school to ask Mrs. Lee for an absence permission for May, bringing the news that May's father has recently passed away and they need to prepare for the funeral. From the conversation, Mrs. Lee also surprisingly learns that this family has never had a cat. It turns out that May refers to her own father as a sick cat. However, the truth of May’s patricide remains concealed from Mrs. Lee, who never finishes the last letter, and Juan who never discovers that the cat is a figment of May's story.