Yurina Kamoshida is a 17-year-old bright and carefree high school student, who doesn't think seriously about the future. One day, Yurina was using her phone and casually downloaded an app called "Servant Shimobee". Since that day, whenever Yurina gets involved in weird situation or trouble, there will be a mysterious middle-aged man who appears from nowhere to help her and leave silently. What is the identity of this man? Meanwhile, Yurina reunites with her good friend from childhood and remembers her dream of becoming a doctor. The dream is unrealistic based on her current academic performance. Will Yurina be able to achieve her dream with the help of the mysterious man?