Suehiro Rika is a well-known and respected brand of a traditional whetstone manufacturer. This 5000 grit stone, known as Rika, has gained widespread fame worldwide.
The stone comes with a small surface-forming stone. The Rika 5000 changes its style according to the amount of water. A 20-minute soaking is often recommended for Rika. Preferably even more, but I have kept the stone submerged overnight with good results.