Multimorbidity is related to ageing and is a growing issue in particular, Japan, where health care needs become increasing and diverse. The RCT remains considered the gold standard for evaluating the efficacy of interventions. However, there is a need for real-world data from unselected patients in clinical practice. Polypharmacy is common in multimorbidity, increasing drug-disease and drug-drug interactions. To choose wisely, there is a great need to create standardized research and interventions to improve polypharmacy and evaluate deprescribing approaches. At this session, we would like to discuss study design and perspects regarding such clinical research in the diversifying era with members.