Wakamatsu

Wakamatsu is a prisoner who got released on parole. However, Iwata from the Oowada gang was jealous and started picking on him. After destroying the toy Wakamatsu made for his child, he raged and assaulted Iwata and ended up badly wounded. Due to Iwata's connection to the guards, Wakamatsu's parole got retracted. 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).