Why I built this.
I'm Toshikatsu Oga. I'm 48. I started as a carpenter's apprentice in Osaka at 15, in 1993.
I spent 30 years on construction sites — first as a carpenter, then site supervisor, then construction manager (the role where you represent the homeowner against contractors). I've watched homeowners get systematically overcharged for three decades. In my direct field experience, overcharges of 20% or more are common, and significantly higher markups are not unusual.
The Japanese term for the worst pattern is "一式" (isshiki) — a single line item meaning "everything bundled together." It's how contractors hide $5,000–$10,000 in margin under one opaque number. There's no legal protection. Architects represent contractors. Lawyers don't know construction. Consumer protection agencies don't have technical expertise.
Two years ago, at 46, I started learning to code. Python first, then JavaScript. Then LLMs and Cloudflare Workers. Then cryptography. The goal was simple: build a tool that actually works at the moment of negotiation, not just produces a nice-looking PDF.
The hardest part wasn't the code. It was realizing the LLM's nondeterminism was structural, not fixable, and that I needed to architect around it instead of fighting it.
Honestly, learning to ship code at 46 was harder than learning to frame a house at 16. I still don't know what I'm doing half the time. But the system runs.
ON SITE
CODING
OPEN DATA
ITEMS