Explore everyday questions with numbers. Practical guides explain how to use our tools and understand the assumptions behind each result.
Money & everyday life
Official sources distinguish the joining month plus 12 prepaid months from an existing member’s current year plus next year. See deduction examples, tax calculations and the 2026 year-end deadlines.
Money & everyday life
Compare ¥70,000 monthly mutual aid contributions with ¥49,892 NISA investments on a similar after-tax household budget. Official index history, reproducible simulations, screenshots, crash risk and loan costs.
Money & everyday life
Compare Japanese income-tax and next-year resident-tax savings from iDeCo, explore ¥23,000 monthly over 30 years, and understand retirement and pension deductions using official sources.
Money & everyday life
Divide 72 by an annual return to estimate the years needed to double a lump sum. Explore compounding and time with a ¥1 million example in the investment simulator.
Money & everyday life
Share your investment simulator plan by link, open an X post, or save a PNG for X and Instagram. Learn how to use your device’s share menu.
Money & everyday life
How much would you need to invest each month to aim for ¥20 million? Explore ¥5,000 and ¥10,000 monthly examples, historical S&P 500 and NASDAQ-100 returns, and the effects of compounding and time in our investment simulator.
