The following exchange is paraphrased from bad Japanese and Ingrish.
Nishi: No, no! He will pay! His insurance will pay!
Nick: Look, I know he might pay, but that'll take ages. It'll be so much easier to just claim it on my travel insurance when I get home.
Nishi: No, not difficult. Mitsui-san, his insurance company will pay! Please give the receipt.
Nick: Okay, if you can guarantee that his insurance company will pay, I'll give it to you.
Nishi: Yes, yes! He will pay. (takes receipt)
"I checked about insurance and insurance company say it is very difficult. They say they need records from hospital. I call hospital but they say they can only give records to Nick only. Insurance company also say that they need proof that i will give money to Nick. so sorry. very difficult."
"I show letter to insurance company but they say they can't be sure it is from Nick. I went to hospital too but they say they have to be careful to stop people commit crime. So sorry. i think very difficult."
Nick cuts a long story somewhat shorter...
Anyway, i finally got Nishi to send the receipt to me and sent it to my travel insurance company with a one-page application form carrying my (ultra-dubious) signature at the bottom.
They returned a cheque for $700 to me within one week. No explanations.No private investigators. No long phonecalls of 2% information transfer, 98% face-preserving pleasantries. No negotiations drawn out by chain-smoking and the inane small-talk which greases the cogs of Japanese communication. No hideous waste of paper in throwing business cards at everyone you have no intention of ever contacting again. No troubles in validating my documents with an oh-so-foreign written signature. No more hissing intakes of breath. No more "velly difficult" or "so sorry". My insurance company didn't even send me an accompanying letter, telling me how they are so "humbly grateful that their humble company has humbly maintained my honourable patronage". They didn't even send me a letter at all. Just a cheque, in a envelope.
It was all I ever wanted.