Tough question: does anyone know where to buy JAPANESE volcanic salt?

A sushi chef once used it and it was insanely good. He said it’s super rare, and that his friend from that island (don’t recall which one) saved some for him, and that it’s usually super expensive.

I know it’s a long shot, but maybe someone here knows a bit about it. Google hasn’t turned up anything for me.

https://www.reddit.com/r/japan/comments/x570mz/tough_question_does_anyone_know_where_to_buy/