Leaving Japan after five years pension refund

I’m leaving Japan after five years of working as an ALT. I got my pension service info in the mail and my wife told me if I claim the refund I would be getting back about ¥400,000. About $4k.

I have paid a total of ¥1,350,000 in the five years I’ve been here. I understand that’s the rule and you only get back a certain amount but my wife says we should leave it here until we eventually come back to Japan which we are hoping to do in maybe 10 years.

Any advice as to wether I can get more of the refund to make it worth while or what to do with the money while it’s sitting here for 10 years not being contributed to at all

Thanks