My JP spouse has USD cash in IBKR and wants to bring this into Japan to fund NISA. What is the most efficient, cost effective method for doing this?

My JP spouse has USD cash in IBKR and wants to bring this into Japan to fund NISA.

What is the most efficient, cost effective method for doing this?

Thank you.

[Clarification] Spouse is JP national and opened IBKR when abroad. All assets sold in advance of return, now sitting in cash. First step is to fund a NISA. Spouse has Shinsei account into which to wire USD or JPY.

by Catcher_Thelonious