Kasumi on hard Jnats is quite difficult to make but possible. You can use Hard Jants for micro-bevel or ura on Yanagi and any single beveled knives, but to make nice kasumi finish is quite difficult. The finish on Harder Jnats will be more finer and more mirror, but still with that nice distinction between hard and soft steel Some super hard stones will scratch your soft steel on knives and ruin your finish, but not all and it also depends on your techniques.
Use as little water as possible but not to little !
Dont use to high pressure !
Your bevel and stone have to be as flat as possible !
Use short strokes while polishing !
Use Nagura if you are beginner to Hard Jnats !
Here are small video of super hard Ozuku Asagi Lv5 + and what finish it produce