Question about Pension and social agreements (leaving Japan)

Hi Reddit!

I’ve looked a lot on this reddit and internet but i can’t find really the reply to my answer.
Kind of specific question.

After 13 years in Japan, i am coming back to my home country, France and work there.

I paid the pension for about 12 years.

I know that Japan have Social agreements with few countries regarding the pension.
Especially it does with France ( https://www.nenkin.go.jp/international/agreement/noteseach/notesfrance.html )

I do read the text agreement as well.

My understanding is that the 12 years I’ve paid in Japan will be converted to the French pension system.(is that correct ?)

And so, at which timing and how i should notify to the Japan pension and french pension my rights?

– At the time of my retirement ?
– Before living Japan ? (To the both country authorities?)

I’m super confused because really it’s an old agreement (2015 ish?) but I could not find any testimony about it and the exact procedures to do.

To whom who did it or knows the procedures, please could you help me ?

Thanks in advance,