Actually, I realized about fifteen minutes after posting that backtracks are confirmed as impossible: the song that brought Doug from Valdemar to MegaTokyo was the first he tried to exit MegaTokyo, and it didn't open any Gate out -- not to Valdemar, not to anywhere. Which still means if he wants to revisit friends he made along the Walk, he'll have to rely on someone else for transportation.
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Big Brother is watching you. And damn, you are so bloody BORING.
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Big Brother is watching you. And damn, you are so bloody BORING.