Togainu no Chi Gaiden

After being devastated in the third World War (known as The Third Division), Japan was divided in two. Several years after the end of the war, a crime organization called Vischio has taken control of the destroyed city of Toshima (formerly Tokyo, Japan's capital city), where they are holding a battle game known as "Igura". The game's main character, a young man named Akira, is falsely accused of a crime. Once arrested, a mysterious woman appears before him, offering him freedom if he agrees to participate in Igura and defeat Igura's strongest man: the king, or "Il-re". The story follows Akira's life in the harsh, lawless Toshima as he fights both to survive and to unravel the mysteries developing around him. 
(Source: Wikipedia)

The main manga adaptation of the game Togainu no Chi.
The Igura: a deadly battle game where players stake their lives in the ruined city of Toshima. In a post-apocalyptic Japan where the underworld rules the day, Akira is placed in jail for murder. He's given a chance at freedom if he can win the game. Whether he finds victory, death, or even love, he will be in for the fight of his life! Based on the ground-breaking bishonen game!  
(Source: Tokyopop)

Based on Nitro+CHiRAL's post-apocalyptic Japan BL game, Togainu no Chi.

A manga adaptation of the game Togainu no Chi: True Blood for PS2.

A Togainu no Chi anthology focusing on Shiki.

A Togainu no Chi anthology focusing on Akira.