Tenpai revolves around a young man named Okimoto Shun, who dropped out of college to become a real mahjong professional. As he goes around Shinjuku, he meets a number of mahjong players, namely a man named Kurosawa Yoshiaki, called the "Mahjong Worker", and his younger trainees. Together, they go through countless rounds of mahjong with the strongest of foes as Shun matures.