Funny, I had a draft lined up of my visit a year ago and I thought maybe it magically appeared 
Thanks for this report! Yeah Kimura was in London and Barcelona with one of the famous Opinionated About Dining jetsetters/models (Aiste herself aka luxeat) along with the chef from Tempura Nitome. Supposedly Kimura had bluefin which he never serves, but given the lack of time to age and him serving relatively fresher or less aged fish is quite interesting indeed.
When I went a year ago, it was about a week after a typhoon had hit Tokyo and there was a shortage of fish, but luckily most of his fish were aged (pre-typhoon purchase). Did not get the fermented crab, but did get that spectacular grilled nameta garei that was not just fatty but had lots of flavor and complexity.
You are very lucky to be able to try that recommended sake. I was just recently told about it, it’s by Ouroku brewery located in Shimane prefecture, and the one you were poured is a Junmai Ginjo nama with a different label “Kei”…王祿溪純米吟釀 for the kanji: it’s either a nama nama or a single pasteurized (the bottle label by the neck would have given this info) and perhaps the back side label of the bottle. Either way I’m told it’s really amazing and this “Kei” was built to pair with seafood. The only US exported Shimane sake that is nama would be Kakeya but a sake sommelier in Tokyo told me Ouroku runs circles around Kakeya and can’t compare (and Kakeya is pretty darn good already). Some sake geeks/retailers in Hong Kong were trying to export Ouroku, but the brewery could not guarantee quality in transit and denied officially exporting any. Ouroku is also only sold in select sake shops across Japan, and thus not as accessible or easy to find. Kimura stocks some very eclectic selections, small producers (and each with their own story), so kudos to him for that. Last year I tried a Junmai Daiginjo that was only sold in one shop in all of Tokyo (I managed to track it down too but got a lower grade more food friendly version).
The oyster butter looks like something he did before (which I did not try) which was taking ayu and grounding it up like a fine paste, maybe not as creamy looking as the butter.
Agreed, Kimura’s rice is specatcular. So much texture and a ton of umami as a result of the organic vinegar he uses from Kyoto.
The Makajiki is typically aged around 48 to 51+ days. While it is the most well known, it was my least favorite during my visit (his aged kohada, kinmedai, and iwashi were highlights for me, and the non aged items that were spectacular: kuro awabi and anago).
Tamago actually contains some aged fish grounded up and mixed in.
I’ll put up my review of last year’s visit when I get a chance!