Shibata's job is to stay in the kitchen's food storage room and watch the inmates as they move the ingredients. It may sound like an easy job, but with the Big Foot Gang and the Black Claw Gang both active there, Young Ben the truck driver's personal dealings with the inmates, and the laziness of Sticks the cook, the job may be much harder than it seems.
You realized that Shibata and Rob the chapel guard look exactly the same. At first, you even thought they were the same one. But after asking, you found out that they are actually twins, and if you look very closely, you can see that Shibata is ever so slightly taller than Rob. But why would twin brothers have such different names? Maybe they have some kind of back story, just like everyone else in here.
As you might have guessed, being the kitchen guard isn't an easy job, but who would have expected that it carries a risk of being killed? As the only guard nearby when the riot broke out in the cafeteria, Shibata unexpectedly found himself in a world of hurt when Alex showed up. And as the only guard injured in the riot, it was because of the beating he suffered that the entire inmate population was locked down for two days. It seems he was just in the wrong place at the wrong time, something you can understand all too well.
