The reward calculation, card annual fees, required spending, temporary promotions, and a worked ¥100,000/month example.
Credit-card investing is worth it when the card is already economical for you and the fund is appropriate; a 1% reward on ¥100,000/month is ¥12,000/year, which a ¥33,000 card fee easily erases unless the card’s other benefits genuinely justify it.
Credit-card tsumitate earns points on your monthly fund purchases, typically up to ¥100,000 a month. To judge whether it is worth it, do one calculation: reward minus the card’s annual fee minus any incremental spending you would not otherwise make to qualify for the rate. Only the net figure is real value.
The gross reward is easy: a 1% rate on ¥100,000 a month is ¥12,000 a year; a 0.5% rate is ¥6,000. These are pleasant but modest sums, and they are the ceiling before any costs are subtracted.
The reward is only worthwhile if the card itself makes sense. Higher reward rates often come from premium cards with annual fees, or require a minimum of non-investment spending on the card. If you pay a ¥33,000 annual fee purely to obtain a ¥12,000 investing reward, you are ¥21,000 worse off unless the card’s other benefits (insurance, lounge access, other points) provide at least that much value you would actually use.
Also beware required spending: a rate that depends on spending, say, ¥1 million a year on the card is not free if it pushes you to spend more than you otherwise would. Count only the benefits you would genuinely use anyway.
Take ¥100,000 a month funded by a card. At a standard 0.5% rate on a low- or no-fee card, you earn ¥6,000 a year for essentially no cost — a clear, if small, win. At an advertised 1% on a card with a ¥33,000 annual fee, the ¥12,000 reward is more than wiped out by the fee unless you separately value the card’s perks by ¥21,000+. And a headline "3%" first-year rate is usually a promotion, not the ongoing rate — separate temporary bonuses from what you will earn every year.
The rule: when the card is already economical for you and the fund is one you would buy anyway, credit-card investing is a nice bonus. When you are choosing the card, the fund, or the spending mainly to chase the reward, it is usually not worth it. Points are a fee rebate, not the reason to invest.
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.