My name is Mifu Miyabi, and I live with my three identical sisters. We're getting closer and closer every day, but we still butt heads sometimes. While we can usually count on our dependable older sister to lead us, she's been acting strange lately. She's rushing out of the house in a panic, staying out really late, and snapping at us... If she won't tell us what's going on with her, there's only one thing we can do—put on our detective hats and trail her to solve this mystery!