He is a doctor and Shio's reformatory director. He constantly pays Ishihara to bring him some prisioner kids, raping them by promising that they'll be free sooner.
spoilerWhen 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 reofrmatory 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 commited suicide and left a suicide note to Sakuragi, telling him all the things that Sasaki and Ishihara did to him.
Sasaki was responsible for Sakuragi's dead.
After the timeskip, the prisioners from cell 6-2 finded out that Sasaki was trying to become President. They manage to make him confess all of his sins and put on during his election's speech. Sasaki is then disqualified from the ellection.
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