Pension options when leaving Japan

I am preparing to move from Japan back to the US. I won't be living in Japan again. I'm trying to better understand my finance options, especially Nenkin. I read this reddit group regularly and find the input helpful.

Situation:

Lived in Japan for 7 years.

Finished job in November, leaving Japan in January.

Paid into company DC plan. I believe I must move this to iDeco account and utilize at age 65.

Paid into Nenkin. This has approximately 5,000,000yen.

Questions:
– What is the best way to handle Nenkin? Lump-sum withdrawal seems like I'd be losing a lot.
– Can I move nenkin to US Social Security? Or keep this in Japan and utilize it at age 65 from the US? – Could Nenkin be moved to the iDeco account and both managed together?
– Do I need to be paying into any pension for the time since finishing my job?

by AgentSuccessful11