[05] When to Pull the Trigger on FIRE — Monte Carlo Says You're Already Free

This is Part 5 of a 6-part series: Building Investment Systems with Python

The Problem with Target Numbers

"You need 25x your annual expenses." That's the standard FIRE rule.

For ¥9.6M annual expenses, that's ¥240M. Most people see that number and think: "I'll never get there."

But the 25x rule assumes a fixed 4% withdrawal rate, zero income, zero adaptability, and a single deterministic path. Real life isn't deterministic. Real life is stochastic.

What if instead of a single number, you had a probability?…