Kakei FIRE — Japan's Family-First Retirement Planner
A FIRE planning app built around Japanese household realities: dual incomes, juku and university costs, kosei nenkin, iDeCo and NISA contribution limits, and severance lump sums, telling couples exactly when they can safely quit without shortchanging their kids.
Japanese dual-income couples in their 30s and 40s trying to plan early retirement while raising children
- FIRE-number calculator that absorbs Japan-specific cashflows including kosei nenkin projections, shakai hoken, kaisei severance estimates, and annual iDeCo plus NISA contribution caps
- Kid-cost modeler with preset cost curves for kindergarten, juku, cram school, and four-year university by prefecture, showing how each child shifts the FIRE date year by year
- Scenario compare for one versus two earners, public versus private schooling, and retiring at 45 versus 50, with a plain-language Japanese summary
The FIRE trend in Japan is explicitly framed around not deprioritizing children, and existing FIRE calculators ignore kosei nenkin and Japanese education costs, leaving a clear Japan-native niche.
Multiple Japanese FIRE simulators (fire-simulator.net, firesim-pro.com, calkita.com, money-keisan.com, waza.tools) attract traffic, and fire-simulator.net has a dedicated family-FIRE guide published 2026-03-07 with concrete figures (couple ¥9.5M, family-of-3 ¥110M), confirming active demand among dual-income parents.家族持ちでもFIREできる？夫婦・子育て世帯のFIRE戦略 ↗FIRE・サイドFIREシミュレーター【2026年版】 ↗
Whites pace is narrower than assumed: fire-simulator.net already covers couple + child scenarios (using 1.3x/1.55x multipliers) and firesim-pro.com already models NISA/iDeCo/pension/monte carlo, while japan-fire-calculator.vercel.app and JPFIRECalc handle Japan-specific assets. Differentiation must come from deeper integration of kosei nenkin + severance + juku/university timelines for couples, which is partially addressed but not holistically modeled.FIRE Simulator Pro | 早期リタイア・資産寿命シミュレーター ↗GitHub - thinknzombie/JPFIRECalc: Japan-specific FIRE calculator ↗Japan FIRE Calculator — Retire Early in Japan ↗
WTP is proven via MoneyForward ME (11M users, paid premium tier), but most FIRE simulators are free and ad-supported, so conversion to paid requires strong differentiation like couple-mode or monte carlo scenarios; freemium with ~¥500-1500/mo premium is realistic.マネーフォワード Me 有料は必要？無料・プレミアムの違い ↗マネーフォワード Me 有料版プレミアム 体験談・メリット ↗
Retirement planning is generational; pension rules change but the planning need is permanent.
Buildable with standard web/app tooling, but requires non-trivial domain expertise in kosei nenkin accrual rates, iDeCo/NISA annual limits, juku/private-school cost bands, and 退職金 estimation; ongoing rule changes (e.g., NISA overhaul in 2024) demand continuous content maintenance.FIRE Simulator Pro | 早期リタイア・資産寿命シミュレーター ↗