Wakamatsu
About
As he couldn't bear it, he hanged himself. While transporting his corpse out of prison, handcuffed, Riki Oh broke his cell's wall and came to Wakamatsu's corpse and broke his handcuffs.
Wakamatsu was just your average Joe. When he was rushing his pregnant wife to the hospital, he accidentally ran over a person and killed him. If he had luck, he'd only get a sentence to the Ichihara Traffic jail. However, he ran over a cop, so he got sent to a B-class prison (for repeated offenders and serial criminals).