Pre-2007 apocalyptic anime I can't remember the title of

So, back in 2006, when Netflix still rented out DVDs, as my mom was setting up a queue, this one anime showed up in the options to choose from. She skipped it, probably thinking an eight-year-old had no business watching it based on the plot alone. It was about a 3-to-6-year-old boy who woke up, went outside his front door, and found that the world had changed for the worst, becoming a nightmarish hellscape—either that or he was isekai'd to an alternate universe. In any case, the series was about him trying to survive in this cruel world—and get home if it was an isekai.