Touhai Densetsu Akagi: Yami ni Maiorita Tensai
One stormy night, Nangou is playing a game of Mahjong with the local yakuza. Soon he finds himself on a losing streak where if he loses, he'll will have to pay with his life. Suddenly, a young teenaged boy named Akagi Shigeru barges in, drenched from the rain. After watching a couple of games, he offers to replace the struggling Nangou. At that moment, a new legend was born.
[Source: Anime News Network]