Ending permanent residence/ pension question

Hello,

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I have a permanent residence visa here in Japan. I’m a US citizen and am considering moving back home.

I know the US has a social security agreement with Japan, and I’ve been paying into shakai hoken for quite some time. If I move back to the US and end my permanent visa status in Japan, will that affect how those funds are transferred to US social security.

I should add that I don’t want to take the lump some withdrawal of my shakai hoken contributions.

Thanks