Cuttlefish That Loves Diving
What if the MC is a hidden transmigrator? he seems to forget about his neighbour and is also familiar with old world terminology.
I don't think so. For mc to be a transmigrater, there should be something in his previous life that can be of significance in this world, for example, a cheat. And cuttlefish will explain if that were so. But mc's current ability doesn't mention anything about another world. Unless cuttlefish thinks that our current world is suited to be inhibited by people of aa post-apocalypse world.