The number of child nodes for removal is finite and small, e.g., an average of approximately 9 in the ZINC dataset, 43 but the number of child nodes for addition is significantly large due to the number of molecules generated by the fragment generation module. Therefore, the selection of some molecules based on some criteria is necessary. In this study, random selection and a criterion for a high value of the evaluation function, such as ϵ-greedy, 44 were selected.