Too late to file 2020 taxes?

During the height of covid (early 2021), I was in the process of leaving Japan under time pressure and didn't get all my affairs in order. I had self employment income in 2020 and didn't file a tax return in February 2021. I came back to Japan in the meantime and I've been reporting all my income and paying taxes correctly.

My income for that year is 15 million yen. Is it too late to file this tax return, what is the procedure like, can I use an accountant or do I have to go to the tax office and beg for mercy, what can I expect from the whole situation? What would a fine look like and is there a possibility of prosecution?

I know that they don't care about anything beyond the most recent 5 years and the window is about to close, but it just feels bad having this type of karma hanging over my head.

by Asleep-Assignment731