Thank you for your email. We hope to continue carrying Yamamoto's knives but regrettably he has slowed down significantly in making knives. His work is a particularly good deal and well made. It is unfortunate that they have become so hard to come by. Yamamoto has become slow enough that we currently wait literally years for his knives to arrive. We have a number on order that we have waited over a decade.
Though Yamamoto is still making knives, he is regrettably not still making the SG2 line. He no longer has any of the steel and has been unable to create the same pattern that Asai was creating. We only have a couple of sizes left and then regrettably this line is done. You are correct that his previous sharpener (Asai's brother) has now retired.
His geometry (as that of his previous master Asai), was truly spectacular. The closest currently, I think is Yoshikane and Wakui.
I had supplied his SG2 when Asai-san was still alive. Regrettably, Yamamoto is slow enough that the quantity makes it impossible to supply the steel (for which minimum quantity is 2 tons).