Akagi

Akagi: Yami ni Oritatta Tensai is a Japanese manga written and illustrated by Nobuyuki Fukumoto. First published in 1991 in Takeshobo's weekly magazine Kindai Mahjong, it is a spin-off of the author's previous work, Ten. It revolves around Shigeru Akagi, a boy who defeats yakuza members well versed in mahjong at 13.