Pricing, minimums, recurring purchases, spreads, distributions, currency conversion, and tax complexity compared.
Index mutual funds price once daily, start from ¥100, and automate easily — ideal for long-term accumulation; ETFs trade intraday with limit orders and can be cheaper for large or specialised holdings, but add spreads, manual reinvestment, and (for foreign ETFs) currency and tax complexity.
An index mutual fund is priced once per day at its net asset value (基準価額), calculated after the order cutoff — so the price you get is not the one displayed when you order. At online brokers the minimum is often just ¥100, and recurring monthly purchases are simple to automate, which makes funds the natural tool for steady accumulation.
An ETF trades on an exchange at an intraday market price, so you can use limit orders and control your entry price. The trade-off is that you bear the bid-ask spread as a cost, and recurring automatic purchases are available at some brokers but far less universal than for mutual funds.
Distribution behaviour differs. Many Japanese index mutual funds retain and reinvest income inside the fund, which compounds automatically and simplifies long-term holding. ETFs commonly distribute cash, and unless your broker offers automatic reinvestment, you must manually reinvest each distribution — a small but recurring task.
Currency adds another layer. A yen-denominated mutual fund embeds any currency conversion inside the fund. A foreign ETF may require you to convert yen to the foreign currency directly, incurring an FX spread, and foreign distributions can carry source-country withholding. For a yen investor, these operational and tax details often outweigh a tiny fee difference.
For most beginners accumulating monthly in NISA, an index mutual fund is simpler: ¥100 minimums, easy automation, embedded reinvestment, and no spread or manual FX. This is why the standard beginner path centres on one low-cost index fund.
ETFs earn their place when you want intraday control, limit orders, portability, specialised exposures a fund does not offer, or lower cost on large trades. Many investors use both — funds for the automated core, ETFs for specific satellite holdings — choosing per goal rather than declaring one universally better.
Brokerage (NISA/iDeCo) · Rakuten Securities
A leading low-cost brokerage for NISA and index-fund investing, integrated with Rakuten points and Rakuten Bank.
Fees: Many domestic funds and trades are low- or no-commission — verify current fee schedule.
Brokerage (NISA/iDeCo) · SBI Securities
Japan’s largest online brokerage by accounts, with a very broad low-cost fund lineup and full NISA/iDeCo support.
Fees: Many trades and funds are low- or no-commission — verify current fee schedule.
Brokerage (NISA/iDeCo) · Monex
An established online brokerage often chosen for US-stock access and research tools, with NISA and iDeCo support.
Fees: Commissions vary by product; some funds/trades are low-cost — verify current schedule.
This is education, not a recommendation. Most beginners research low-cost, broadly diversified index funds — for example all-country (全世界株式) or S&P 500 trackers — rather than picking individual stocks, because low fees and diversification are within your control while returns are not. Understand that values fall as well as rise, match the risk to your time horizon, and never invest money you may need soon.