The COVID-19 pandemic has had negative psychological effects, such as increased depression, anxiety, and suicide, on children worldwide, including in Japan. To effectively mitigate the negative impact of the pandemic among Japanese children, it is necessary to increase understanding of the culturally specific psychological effects on Japanese children, including age and gender differences, as well as related risk and protective factors. However, no previous research has quantitatively evaluated changes in Japanese children's emotional functioning before and after the pandemic began. The present study examined changes in Japanese children's emotional functioning with pre- and mid-pandemic questionnaires, particularly focusing on age and gender differences. The present study also explored the effects of school adjustment, social interactions, and lifestyle activities on children's emotional and behavioral functioning during the pandemic. Data were analyzed from 293 children from the southwestern region in Japan. The pre-pandemic questionnaire assessed emotional and behavioral functioning and school adjustment, while the mid-pandemic questionnaire assessed emotional and behavioral functioning, social interactions, and lifestyle activities. The results indicated that the COVID-19 pandemic negatively impacted the emotional functioning of Japanese children, especially younger boys. Pre-pandemic school adjustment negatively influenced emotional functioning. Spending time alone, spending little time with one's mother, poor sleep regulation, a lack of exercise, and a high frequency of playing video games were related to poor emotional and behavioral functioning. The findings imply that Japanese children, especially younger boys, may benefit from psychological interventions that promote social interactions, especially with their mothers, regulated sleep patterns, adequate exercise, and that support children in managing video game engagement, to mitigate the pandemic's negative psychological impact.
