I was alerted that this pop-up was going on at Tokyo Fish in Berkeley. For $9, I got a flavorful bowl of mild broth, a couple of slabs of roast pork, nori, a medium-boiled egg and various garnishes.
(not my photo)
He also has more intense versions of the broth, and I wish I’d written them down. There’s seating for about five people on a folding table.
I stopped there a few months back and it was a nice bowl. I wish I had known he was going to be there today, because I went by when he was setting up to pick up some things for lunch and dinner, but too early for a bowl.
It’s too bad that the web page doesn’t include a schedule. I guess you have to follow him on Twitter to get the news.
He’s no longer going to be at Toyko Fish Market. 
He is still at the Kensington farmers market on Sundays. I think I’ll head up there next week to ask him about his plans.