It is desirable that a 3D city model at level of detail 2 (LOD2) has texture images mapped on building surfaces. Owing to the cost of image collection, it would be the best way to use aerial images for texture mapping at present. Although aerial oblique images provide higher-resolution texture images, using aerial oblique images has a major issue of occlusion. Accordingly, we develop software for texture mapping to a 3D city model using aerial nadir and oblique images, aiming to minimize the impact of occlusion. The software designed to be used in ordinary operation includes the features of automatically detecting occlusions on building surfaces within images by utilizing the geometry of a 3D city model and automatically selecting appropriate oblique and nadir images for texture mapping. The major feature of the developed software is its ability to process grid by grid on a building surface. The validation experiment results confirm the software's satisfactory performance in practice. Moreover, the experiment results indicate that the performance of the software depends on the ability of a 3D city model to represent buildings. Since we have recognized that it would be effective if each pixel of a texture image has its own resolution, we plan to modify the software so that each pixel can have its own resolution.