Na-na-na-nah! Na-na-na-nah! Welcome to after the end!
Ya sure about after 'the end'? Because in the latest episode the Foxes said something about Hunters, those who eliminate Ceruleans. And in the same episode you can hear Kaban's voice interpoised with the Park Guide's recorded voice (yea, Boss in the green-eye mode are basically a voice-playback device). It could be that the Park they're in is not the main park, rather a sub-park like Jurassic Park's Isla Nueva or something that has fallen because the Ceruleans, so the tourists abandoned it. From the state of the bridge and the library, it seems considerable time has passed since the abandoning, so there's a huge question why Kaban still at that age. There's also speculation that the Ceruleans are humans that are exposed by the Sandstar too much and ended up mutating as blobs; even if they lost the consciousness they still partly remember what job are they doing. For example, the first Cerulean at the area gate might be a gatekeeper, the Ceruleans at the underground maze are trapped tourists, the Ceruleans at the Snow Mountain is skiiers.