This thread gets linked from time to time so I'm just going to post a summary of the results(skipping the reasoning which can be found in the long posts)
For all japanese funds, either use morningstar or
http://shintaro-money.com/index-cost/ to find the real calculated costs.
Lately eMaxis have slashed costs and seem very good, but tawara, nissei and others offer very competitive rates too.
Investing in total world:
Use a japanese fund that is NOT a fund of international etfs(e.g. if it is packaging VT inside it that's no good). This is to avoid triple taxation. Nissei or tawara or whatever is fine. Generally these track MSCI kokusai ex. japan so if you want real world coverage you should buy up a japanese fund separately. eMaxis slim works here
Investing in US:
Best option is probably buying straight up VOO or similar. Whether you use a US ETF or japanese fund, you'll be taxed twice, and vanguard has lower costs.
If you can't buy VOO(broker doesn't have it or for iDeco), whatever lowest cost fund you can find will work(fund-of-funds are fine here). For rakuten iDeco the rakuten-voo option would be acceptable. For SBI I believe the equivalent is the i-exe offering(?)
Investing in japan:
Lowest cost domestic fund you can find. Tawara is good
Investing in emerging markets:
again lowest cost domestic. AVOID fund-of-international-funds(e.g. stuff like vanguard emerging markets) which will get triple taxed. eMaxis slim is good
ETF vs traditional funds:
Many low cost index funds reinvest dividends internally. This means they generate zero dividends but their value increases instead. This means you get to effectively defer taxation until you sell. With compounding this means that funds that are somewhat more expensive than ETFs will still come out ahead of the ETF if you are holding for a long time(talking at least 5+ years here, generally decades), making them better for buy and hold strategies. Really, if your holding horizon is years, you should probably be using ETF's, if it's decades, traditional funds.
Additionally, using funds instead of ETF's allows you to "expand" your tax free bracket inside your nisa/iDeco accounts.
If I missed anything important I'll try to update it here.
Finally, I'm in no way a professional, this is all just what I figured out from research, translating blogs etc. I can't take responsibility for any losses from this advice, but my personal investments are entirely in line with it
