Don: Gokudou Suikoden
Japanese title: ドン 極道水滸伝
Type: OVA
Source: Unknown
Episodes: 2
Status: Finished Airing
Aired: Jul 1, 1992 to Sep 9, 1992
Duration: 50 min per ep
Rating: R+ - Mild Nudity
Studios: J.C.Staff
Genres: Drama
Themes: Organized Crime

Takekichi and Masakazu are two tough guys who are forced to go underground when they lose their boss in a turf war in this modern update of the classic Chinese novel "Water Margin". 

(Source: The Anime Encyclopedia)