This chapter focuses on the impact of the COVID-19 pandemic on Japan and the social and mental health challenges faced by the Japanese people. The government and society’s response to the infection included the encouragement of behavioral restraint and the promotion of non-pharmaceutical interventions (NPIs), such as the wearing of masks and social distancing. These NPIs have been effective within the cultural adaptability of Japan in reducing the spread of infection. However, despite these efforts, restrictions on social life caused problems such as isolation and psychological distress. The role of social norms and cultural context in adherence to preventive measures, the psychological and social consequences of loneliness and isolation, and the impact of telework and alcohol consumption on mental health are also highlighted. This chapter also touches on the prejudice and mistreatment associated with COVID-19 and emphasizes the need for appropriate communication and support to manage the psychosocial effects of the pandemic. It suggests that while Japan’s collective response helped to contain the spread of the virus, it also posed significant mental health challenges, underscoring the importance of striking a balance between infection control and mental health support.