We demonstrated that crystal graph similarity between IS and FS plays an important role in IS2RE task (Figure ). The plot showed V-shape behavior for the prediction accuracy of IS2RE task, indicating the existence of the optimal graph similarity. We note that a location of the optimal point, the vertex of 'V', depends on the dataset, since the graph similarity and prediction accuracy of models are affected by the difference of representations of IS and FS. For example, if there are many data whose atomic positions of IS barely change during geometry optimizations, i.e., configurations of IS are very close to the ground state, the optimal point will downshift toward models with specific geometry information, like CGCNN-HD. Conversely, if there are many IS whose configuration is very far from RS, the optimal point will upshift toward Wren/Roost (Figure ). Nevertheless, we expect that the IS2RE task error with respect to the graph similarity will always be V-shape regardless of test dataset.