The breakup of a liquid droplet exposed to a high-speed airflow has several engineering applications such as liquid fuel atomization and chemical processes. We have been developing a particle-grid hybrid analysis method to simulate liquid atomization at an acceptable cost. In the method, the liquid is analysed by the moving particle simulation (MPS) method, and the airflow is solved by the finite volume method (FVM) using a relatively coarse grid. This time, we improved our method by utilizing the immersed solid (body) method (ISM). The gas-to-liquid aerodynamic force was evaluated by the pressure field solved by the FVM. In addition, when the FVM grid was too coarse to capture the airflow past a droplet, we added to the aerodynamic force the pressure distribution of the flow past a sphere. We simulated droplet breakup to validate the present method. The breakup modes known from experiments, namely bag breakup, multimode breakup, and sheet-thinning breakup, were all predicted at their corresponding Weber numbers. Using the ISM improved the airflow field and hence the aerodynamic force estimation. The present method, which can solve liquid atomization even when using a coarse grid, will enable industrial engineers to directly simulate real-world atomization problems, understand the underlying physics, and improve their products.