First Yoshida san explained me his forging.
He put the two deba he forged on the table. He explained showing the front side (omote) that the next step is grinding before the heat treatment (HT). After grinding the yellow broken line will become the shinogi.
I found a border line at the backside(ura) and asked him if it is the border of jigane and hagane (jizakai). He answered yes. Then he draw a line (the red broken line) with his finger and said with a modest smile:" For top line knives the jizakai is here. You put more hagane on and most of the ura is hagane"
I asked if he will grind the ura to make it concave.
"To hammer the steel is very important. It becomes better steel. Even stainless steel will get better. The resulting kitchen knife cut better, it is easier to sharpen and it will hold the sharpness longer"
Then he left to search something. He came with a piece which would be a santoku I think.
And indeed I could only find thick bars in the workshop.
to be continued....