The rapid increase in users of application (App) for smart device during disasters and emergencies necessitates realistic and large-scale simulations. Existing methods using physical devices or emulators face challenges in hardware dependency and overhead, making the simultaneous execution of millions of App difficult. This study proposes a method for constructing “vApp,” headless App that can be executed as back-end processes independent of GUI. By leveraging design patterns of GUI application, the front-end is rebuilt while retaining the logic for processing user inputs. Collaborating with a multi-agent simulator (Agent) allows appropriate simulation of user operations and environmental information, enabling the construction of a large-scale automated execution environment. Evaluation results demonstrate that the proposed method outperforms conventional methods in terms of computational resource efficiency, time reduction, execution cost savings, and scalability.