Kashio Rigen
Kashio Rigen (1565-?) was one or more Go players.
Rigen was the rival of Honinbo Sansa and the teacher of Monnyusai.
In a Hikaru no Go chapter, Hikaru Shindo (the protagonist) stars as Rigen in a school play.
John F. There was almost certainly no such game and no person Kashio Rigen. See "The Go Companion".
tapir: Can you elaborate a little further?
Herman: The Go Companion, on page 198-199, quotes a text which mentions Rigen and Kashio as different people, and goes on to explain that in all probability, the name Kashio Rigen is a confusion based upon another text, in which those names are right next to each other.