Expat in Japan: how to start investing

Hi everyone,

I’m a European citizen currently living and working in Japan.
I don’t have permanent residency yet, but I plan to stay a few more years before eventually returning to Europe.

All my savings are still in Europe in a traditional bank, and I’d like to start investing while I’m here — mainly for long-term growth.

I’ve heard about NISA and iDeCo, as well as Interactive Brokers (IBKR).
However, I’m a bit confused about what makes the most sense in my situation:
• Can I open a NISA account even without permanent residency?
• Is iDeCo worth it if I might leave Japan in a few years (since it locks money until 60 if I understood it correctly)?
• Is IBKR Japan a good option for expats who may move between countries later?

Ideally, I’d like something simple, tax-efficient, and that I can keep managing after I return to France.

If anyone has experience as an expat in Japan investing internationally, I’d love your advice!
What would you recommend as a good starting point — NISA, IBKR, or something else?

Thanks a lot 🙏