One of the most famous challenges was by Higaki Koreyasu (檜垣是安), who challenged Meijin Oohashi Souko II in 1652, and Itou Soukan was there to accept it as the Meijin’s iemoto proxy.
Soukan had given Koreyasu bishop handicap and lance handicap games many times before. The bishop handicap games were all won by Koreyasu and the lance handicap games by Soukan. Koreyasu now intended to take on and defeat Soukan in an even game, preparing a secret new “gangi” strategy to do so.
In an even game, Soukan as the senior player would move second, and very likely would play ranging rook as the theory of the time suggested; Koreyasu’s gangi strategy was a countermeasure to this, preparing a static rook with a bishop retreat to 79 aiming at 24. He was supposedly inspired by the steps of a riverbank berth for boats, called gangi (雁木); the other pieces formed a staircase shape to leave the bishop’s diagonal from 79 to 24 clear.
However, in accordance to Souko’s wishes, Soukan and Koreyasu would instead play a two-game match, one with a right lance handicap and one with a bishop handicap. The choice of which game would be played first was up to Koreyasu. As uwate (the handicap giver) would typically play static rook, Koreyasu’s gangi strategy would not see the light of day.
The match proceeded in the 8th month of 1652, Koreyasu choosing to play receiving a right lance handicap first. In a double static rook game, Koreyasu used silvers on 67 and 57 along with a sleeve rook (sodebisha) attack to win.
Winning the lance handicap game gave Koreyasu an enormous boost, and at once made a threat to the authority of the shogi houses. If Soukan were to lose the next game and the match at bishop handicap as well, it would damage the reputation of the houses (including Meijin Souko whom he was representing), and embolden even more challengers. This next game was a must-win game for Soukan.
Three days after the first game, the players locked horns in battle again, neither side willing to lose. A wild fight started from Koreyasu’s third-file rook opening, with the initiative changing sides several times during fierce attacks by both players. Finally, after a marathon 161 moves, Koreyasu resigned. Soukan had defended the authority of the houses once again.
According to folklore, this second game left Koreyasu mentally and physically exhausted, vomiting blood no sooner than he had resigned. This story is well-known even today, and the game is known as the “blood-vomiting game” (吐血の一局).
Koreyasu’s original gangi strategy, conceived to challenge the houses, never saw the light of day in an official match. But instead through some misunderstanding, the twin silver strategy he employed to win the first game came to be known as gangi, even though he was not the first to use it. Here gangi was interpreted as a snowroof (also 雁木, written the same way), the shape of which is represented by the two silvers on 57 and 67 and a gold on 78.