Trading commissions, FX spreads, NISA support, available securities, extended hours, research, US-taxpayer restrictions, and withholding.
For US stocks, SBI, Rakuten, Monex, Matsui, and IBKR Japan lead on NISA support and competitive trading/FX; compare the 0.495%/US$22 commission model and FX spreads, note that US dividends carry US withholding even in NISA, and check US-person restrictions.
For US stocks, several large brokers share a similar model: about 0.495% commission on taxable trades, capped at roughly US$22, and ¥0 on NISA-covered US shares and ETFs. So on cost, SBI, Rakuten, Monex, and Matsui are broadly comparable, and the FX spread often matters more than the commission — some advertise a zero real-time USD/JPY spread, others a per-dollar spread. Verify current conversion terms.
IBKR Japan uses a different, professional pricing model with interbank-style currency execution plus commission, and supports eligible US products in NISA. It suits investors comfortable with a professional platform and broad global access.
Beyond cost, compare the available securities (the exact tickers and ETFs), extended-hours trading, and research tools. Monex is noted for strong US-stock research, screening, and analytical tools; moomoo and Webull offer data-heavy, active-trading-oriented platforms; IBKR offers the widest global reach. If you trade specific US names or want after-hours access, check each broker’s exact support.
For a passive investor buying a US index fund monthly, most of this is secondary — a low-cost fund at a mainstream broker does the job. The advanced US-stock features matter mainly to more active or research-driven investors.
Two cross-border points are essential. First, US dividends carry US source-country withholding even inside NISA — NISA removes only Japanese tax — so model the after-withholding yield. Second, US persons face restrictions: Rakuten, for example, states US persons may not trade its foreign-stock products, and other brokers impose different rules. If you are a US taxpayer, confirm the broker accepts you and get cross-border advice before buying.
For non-US persons, the main choice is cost, FX, and platform; for US persons, broker acceptance and US tax treatment come first, and US-domiciled ETFs bought at a permitting broker may be simpler than Japanese funds.
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.
Be very careful. Japanese mutual funds and ETFs are usually PFICs (Passive Foreign Investment Companies) for US tax, which triggers punitive US taxation and heavy Form 8621 reporting — and the NISA tax exemption does not apply to the US. Many US persons in Japan avoid Japanese pooled funds and instead hold US-domiciled assets, but rules are complex. Get advice from a cross-border US/Japan tax professional before investing.