This #3000 grit whetstone has worked well in my tests. I have noticed that the Ouka has fallen a little behind its more famous big brother Rika 5000. However, I haven't come up with a negative about this stone yet—an brilliant, pleasant stone to use.
Ouka works in the same way as Rika, which means you can adjust the amount of water you use to adjust the style of the stone. It needs at least a 20-minute soak to work well, but I have used even a short soak and additional water as needed.