Do I still need to give up my old nationality to become a Japanese citizen?

I was born and raised in Germany and lived in Japan now for already 15 years and am married to a Japanese woman since 10 years. My Japanese is also good enough although far from perfect.

So I think I would qualify to become a Japanese citizen easily, but in the past neither Germany nor Japan allowed to have dual citizenship. However in Germany that has recently changed and you can have dual citizenship.

As far as I know Japan still don’t permit that, but will they actually check and confirm that I have ended my original citizenship or are here perhaps some people who managed somehow to have dual citizenship?

I would like time to get the Japanese citizenship as I also have 2 children, but giving up my old one is a big ask, since it opens me the door to every country in the European Union, since you never know what the future brings and citizenship has only minor advantages (the right to vote) compared to the permanent resident visa.