Why Japan has so much debt?

Excuse me, I'm a bit confused about Japan's economic situation. I've heard that Japan has a significant amount of debt, and I'm wondering why that is. Could you please explain the reasons behind this high debt level? Is it due to years of fiscal spending, or are there other factors at play? And, given this high debt, what are the potential implications for Japan's economy and its future? Thank you for your time and expertise.