Japan is facing a number of issues, from economic struggles to population decline and environmental problems. This article examines the various challenges that Japan is currently facing and discusses what its biggest problem is today. It looks at the country's economic struggles, population decline due to low birth rates and aging society, poor work-life balance, lack of diversity, gender inequality, and environmental issues. The conclusion is that Japan's biggest problem is population decline due to low birth rates coupled with an aging society, which could have serious implications for quality of life and economic activity if it continues unchecked.