Configure default assumptions and tax rates. These apply to all new scenarios.
Override Japan's built-in tax rates. Changes affect all scenario calculations.
Combined income + residence tax on investment gains. Japan default: 20.315% (15.315% income + 5% residence).
Applied on top of income tax. 2.1% until 2037 (East Japan earthquake reconstruction).
Flat rate on taxable income. Standard: 10% (6% municipal + 4% prefectural).
Annual fixed per-person levy. Standard: ¥5,000 (¥3,500 municipal + ¥1,500 prefectural).
Assumed annual rate for mortgage amortisation calculations. Japan average: ~1.5%.
These values pre-fill the assumptions form when creating a new scenario.
Expected annual return during accumulation. 5–7% typical for global equity.
More conservative after FIRE — usually 0.5–1% below pre-retirement.
Standard deviation of returns. 15% typical for global equity.
Results compare this with a Monte Carlo-derived safe rate for each scenario.
Recent Japan CPI has been ~2–3%.
Typically below general inflation — retirees often spend less over time.
Pre-fills the region for new scenarios. Can be changed per-scenario.
Default NHI municipality for new scenarios. NHI rates can vary up to 2× between the cheapest and most expensive municipalities.
Default number of people covered under NHI. Each additional member adds a per-head levy to the annual premium.
Default USD/JPY rate pre-filled for new scenarios. Update when the rate changes significantly.
1,000 is fast; 10,000 gives stable statistics.
How many years of retirement to simulate.
Amplifies volatility in early retirement years.
Which FIRE strategy is highlighted by default in new scenario results. All variants are always calculated regardless of this setting.
How yen values are displayed in charts.
Sets the default display language. Can be switched at any time using the language toggle in the navigation bar.