This is the knife chef Jun Yukimura (Azabu Yukimura, 3* , Tokyo) uses , particularly for shearing pike eels (hamo) bones. The knife comes from Aritsugu, a 450 year old producer from Kyoto, who originally produced swords for samurais. When I asked to hold it, I felt I was holding danger - the knife is very very sharp!
P.S. Back to Japan!