The story revolves around the mahjong gambling exploits of Shigeru Akagi (赤木しげる Akagi Shigeru?). After a death-defying game of chicken one evening in 1958, Akagi nonchalantly enters a yakuza mahjong parlor to shake the police’s trail. Although he is unfamiliar with the rules of mahjong, his gambling intuition saves a small time gambler, Nangou (南郷), and grants him a seat at the gambling table. As the night progresses, the stakes are raised both within the game and for Akagi, who is under the suspicion of the local policeman, Yasuoka (安岡). However, Akagi manages to defeat Keiji Yagi (矢木圭次 Yagi Keiji)—despite Yagi’s cheating during the game—and impresses the members of the gambling house.
Yasuoka arranges a new match against other yakuza members, in which Akagi defeats Ichikawa (市川?), a blind professional mahjong player with very accurate hearing. After defeating him, Akagi gains mythical status at 13 but then disappears, becoming a legendary figure all over Japan. Six years later, Yasuoka orders Yukio Hirayama (平山幸雄 Hirayama Yukio) to pretend to be Akagi to impress some yakuza bosses and make money. Meanwhile, Nangou finds the real Akagi, now aged 19. Akagi, however, does not need to play with Hirayama as Hirayama is defeated by Urabe (浦部), a professional mahjong player for another yakuza group who is later defeated by Akagi.
Akagi’s ultimate rival is Iwao Washizu (鷲巣巌 Washizu Iwao), an old man who has made a lot of money and become one of the most powerful people in the Japanese underworld. Having built up massive funds from shady dealings in Japan’s post-war era, Washizu tempts people to bet their lives for the chance to win a large amount of money. Washizu and Akagi play mahjong in an unusual way that Washizu calls “Washizu Mahjong”, in which glass tiles replace most of the tiles and make the game different in many ways.