Harder material means, it would be also harder to sharpen it.
Generally speaking, most of Japanese Manufacturer don't disclose any HRC rating and the rating shows that of base materials themselves from Steel Manufacturers.
It is similar to the relationship between Food stuff and the Cook. Are you confident of good cuisine, because it is made of good stuff? The answer is YES or NO?
Don't forget superior technique of the Cook!!! The genuine sharpness would be different after heat treatment, depending on workshops or brand, even if they use the very same materials. Therefore, please look for your favorite brand, first of all.
Yoshi Sakamoto/ Shop manager YuiSenri