This study examined Japanese childrens’ relationships with their parents and peers over time during the COVID-19 pandemic. 425 parents served as proxies for their children aged 0-9 years and completed the Strengths and Difficulties Questionnaire (SDQ) at three time points: during school closures and lockdown measures; after lockdown measures were lifted; and during a state of emergency declaration where schools were allowed to remain open. The authors used the Inclusion of Other in the Self (IOS) scale to evaluate the overlap of participants’ perceived self-parent and self-other boundaries. Children in preschool and grade school demonstrated increased problematic behavior during lockdown compared to after lockdown. Overall, IOS scores for child-parent relationships were higher across all ages during lockdown measures, and scores for child-other relationships were lower during lockdown measures across all ages. The authors note that the changes in child-parent and child-other relationships were not significant for infants and preschoolers. They suggest that, since the parent-child relationship is fundamental to developing social interactions for these age groups, social isolation was less influential on infants and preschoolers because their main relationship with their parents remained stable.