Iwata, from the Oowada gang, is one of the big shots in the prison. He likes picking on the weak, so Wakamatsu easily ended up being his victim. However, he didn't have much luck as he ended up messing with Riki Oh. Ending up hurt by Riki Oh, he plotted revenge, which ended tragic for him.

In the late 1990s, society is descending into ecological collapse and totalitarianism. Saiga Rikioh, 21, finds himself in jail. 
Set in the near future, at the privately-owned Tokyo State Prison. Like the chilling wind of the end of a century, a mysterious man with a six-pointed star on his fist entered the pen. 
Saiga Riki-Oh--serving a term of three years, due to assault, his first offense. Riki-Oh openly antagonizes The Four Emperors, four powerful prisoners that control the prison and keep the rest of the inmates in line.

A Retelling of the prison arc of the manga RIKI-OH! 
The story follows Saiga Riki-Oh, a young man blessed with inhuman strength. After taking revenge against a yakuza boss who was responsible for the death of his girlfriend, he ends up in a maximum security prison owned by a private organization. 
The prison is divided into four blocks, each run by a member of prisoners known as the Gang of Four. The first member is a tattooed knife wielder known as Hai that runs his block in a mafia style family system. The second member is a giant man (known as Tarzan in the live action) with incredible strength. The third member is a effeminate fighter named Huang Chaun that is growing Opium in the prison. The final member is a small man that use sewing needles as his weapons.