Yasui Sanchi
Yasui Sanchi (安井算知, 1617–1703) was a Japanese professional Go player, and second head of the Yasui house.
He became Meijin-godokoro in 1668. It has always been said[1] that this promotion was achieved by a backstairs route, with influence exerted by the head of the Matsudaira clan. A related anecdote[1] has Hon'inbō San'etsu facing down Lord Matsudaira during an earlier official oshirogo against Sanchi.
The Hon'inbō house did not take this lying down. From 1668 to 1675 Hon'inbō Dōetsu played a twenty-game match against Sanchi (they had played in 1649, but after that there was a dearth of competitive games). Dōetsu had the better of it with Black, earning the right to a game with White (as at sen-ai-sen).