Leaving with 9 years of paid pension time vs staying until 10 is reached?

Hello!
I’m planning to return to Germany for good and currently have about 9 years that I paid pension in Japan.
I know that Germany has an agreement with Japan to count that time period when I return, but I also recently learned that if I hit the 10 year milestone I become eligible for receiving pension payments directly from Japan upon retirement.
(I’m in my 30s so it’s still a while until then)

I’m wondering if anyone has gone through the process and has insight if it would be worth it staying until I reach the milestone?

Can I just contact a local 年金相談所 about things like this…?