More than five millennia ago, a man tried to unite all civilization under a single city: Babylon. The city became a legend, then a myth, then an absence — not even ashes remained. By 2014, a technologically advanced civilization has long since filled the gap. A prestigious institution called The Golden Age is celebrating its twenty-fifth anniversary, inviting students from across the world to its event. The plane carrying them disappears mid-flight. Ryoga Kanzaka, a Japanese student selected for the trip, comes back to awareness in a city that identifies itself as Babylon — a city that should be impossible to stand in. The walls around what everyone believes they understand about the world are thinner than they appeared.