He constantly pays Ishihara to bring him some prisoner kids, raping them by promising that they'll be free sooner.
When Sakuragi entered the reformatory, he had a cellmate named Eiichi Hagino. Hagino's mom was very sick, so he wanted to get out of the reformatory as soon as possible. Sasaki then promised Hagino that he would let him go sooner if he had sex with him. Of course he was lying. When Hagino discovered Sasaki's lie, he committed suicide and left a suicide note to Sakuragi, telling him all the things that Sasaki and Ishihara did to him.
After the timeskip, the prisoners from cell 6-2 found out that Sasaki was trying to become the Mayor. They manage to make him confess all of his sins, which they record and let everybody hear at his election speech. Sasaki is then disqualified from the election.