So some of the skins are now wet... and they're in a burning building presumably full of iron machinery. All head jailer needs to do is accidentally bump into a machine while trying to escape the fire. Fakes revealed.
Wasn’t Tsurumi the one to say the code might never be found if one prisoner dies? Or maybe he was just lying then and didn’t actually believe it himself. Iirc he was trying to get someone to stop searching for it