Also known as: 鷲巣麻雀
A variant of Mahjong invented in the Akagi manga and named after its creator, Washizu Iwao, which involves a special tile set in which three out of four of each type of Mahjong Tile are transparent. Instead of a wall, tiles are drawn from a hidden container while the players wear Black Gloves to make sure they can't feel the tile. In addition, points can be paid for with Blood or Money.
It is the centerpiece of the titular Washizu Mahjong arc of the manga, which is composed almost entirely of the mahjong game between Washizu Iwao and Akagi Shigeru. The arc lasted between 1997 to the manga's ending in 2017, making it the longest arc and the longest "battle" in manga history.