Edit Assumptions — My Scenario

Scenario Details

Scenario Name *

Name this scenario so you can compare it with others — e.g. 'Base Case' vs 'Pessimistic Returns'.

Cost-of-Living Region

Sets your cost-of-living baseline. Changing the region updates the monthly expense estimates used in the FIRE number.

Description (optional)

Investment Returns

Global equity blend. Nominal, yen-denominated.

Pre-Retirement Return (%)

Expected annual return during accumulation. 5–7% is typical for a global equity portfolio.

Post-Retirement Return (%)

More conservative after FIRE — usually 0.5–1% below pre-retirement return.

Annual Volatility (%)

Standard deviation of returns. 15% is typical for a global equity fund.

Withdrawal & Inflation

Safe Withdrawal Rate (%)

Results compare this with a Monte Carlo-derived safe rate for this scenario.

Japan Inflation (%)

Recent Japan CPI has been ~2–3%. Your expenses grow at this rate in retirement.

Retirement Expense Growth (%)

Typically below general inflation — retirees often spend less over time.

Foreign Pension Inflation (%)

Growth rate for foreign pensions (US Social Security, UK state pension). Tracks home-country CPI, not Japan's. US ~2.5%, UK ~2.0%.

FIRE Variant

Selects which FIRE target is highlighted in results. All variants are always calculated.

FIRE Strategy

Highlights the selected variant's FIRE number in the results hero. All variants are always computed for comparison.

Regular FIRE: Retire when your portfolio covers standard living expenses via the safe withdrawal rate. The baseline approach.

Lean FIRE: Retire sooner on a lean budget (default 70% of regional expenses). Lower target, tighter spending.

Fat FIRE: Retire with a generous lifestyle budget (default 150% of regional expenses). Higher target, more comfort.

Coast FIRE: Save enough now so that compound growth alone reaches your FIRE number by a target age — then stop saving and just cover expenses.

Barista FIRE: Retire with a smaller portfolio by supplementing with part-time income. Work part-time doing something you enjoy.

Lean: Monthly Budget

¥

Your lean monthly living expenses. Leave at 0 to use 70% of the region template as default.

Fat: Monthly Budget

¥

Your generous monthly lifestyle budget. Leave at 0 to use 150% of the region template as default.

Coast: Full Retirement Age

The age you stop working entirely — your investments must reach the FIRE number by then.

Barista: Monthly Part-Time Income

¥

Monthly income from part-time work during semi-retirement. For JPY300,000/year, enter JPY25,000/month. This income is modelled as continuing indefinitely; switch to Regular FIRE assumptions if you plan to stop working later.

NHI (National Health Insurance)

NHI premium is a function of your withdrawal — we solve for this iteratively.

Municipality

NHI rates vary significantly by municipality — up to 2× between cheapest and most expensive.

Household Members on NHI

Each additional member adds a per-head levy.

Monte Carlo Simulation

Number of Simulations

1,000 is fast; 10,000 gives stable statistics. More = slower but more accurate.

Simulation Years

How many years of retirement to simulate. FIRE at 45 → model to 95 = 50 years.

Model Sequence-of-Returns Risk

Amplifies volatility in early retirement years — the most dangerous period for early retirees.

Mortgage Rate Model

Mortgage Rate Stochastic Model

Model Variable Mortgage Rates

If enabled, variable-rate Japan mortgage payments are stress-tested with a mean-reverting rate path in Monte Carlo. Fixed mortgages are not varied.

Long-Term Mortgage Rate Mean (%)

Mean reversion target for stochastic mortgage rates.

Mean Reversion Speed

Higher values pull rates back to the long-term mean faster.

Mortgage Rate Volatility

Annual standard deviation in absolute percentage points.

Foreign Exchange

USD/JPY Rate

Current USD/JPY exchange rate. Used to convert USD-denominated foreign assets to JPY for the total portfolio calculation.