Kouetsu was a very important figure in the arts of the early days of the Tokugawa Period. He was born into a house of warriors, but became a great artisan, whose calligraphy, lacquer works, publishing, and tea ceremony traditions became noted by even the Kubou, Tokugawa Ieyasu 徳川家康. He became known as one of the "Three Brushes of Kan'ei." He became so well known that he could found his own artistic community known as Kouetsu Village. After his death in 1637, his mansion was converted to a temple of Nichiren Buddhism called the Kouetsu Temple.
Miyamoto Musashi 宮本武蔵 is introduced to Kouetsu by Itou Ittousai 伊東一刀斎, who has been using him to track the man responsible for the deaths of his family and students. To Musashi's surprise, Kouetsu's room is an elevator, leading to a secret, hidden level. There, a host of ninja await. These are Kouetsu's spies, and the source of his information.
Kouetsu proves invaluable to Musashi, helping him throughout the entire game, much like the Hanaya (Kage) character."