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. 20% margin overcharges are normal. 50% happens. 100% isn't rare.
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