500 years, and any buildings still standing, lol, immersion completely ruined. Not to mention edible canned goods. Whatever, it's
Yamada Yoshihiro so the drama will be top tier and the expressions godlike.
I can't speak for the buildings with a degree of certainty, but we have some places where 1000+ year old structures are still standing in some capacity. Look at the Roman Colosseum and the Leaning Tower, not to mention some of the ancient structures throughout Europe, the Middle East, India, Asia, etc. I mean some stuff in South America that are thousands of years old are still standing.
I get it, modern architecture may or may not be still standing after 5 centuries, but the mangaka did show some buildings had collapsed.
As to the canned goods. Depending on where they are stored and how secure the can is, etc. the argument is that they could last indefinitely and still maintain some nutritional value while maybe losing flavor, texture, etc.
Page 13
Why didn't they wake up like he did?
Good question. It seemed to imply that the power was diverted to his hibernation pod/chamber/bed. But you're right, why didn't they just abruptly wake up? The wife was first, why didn't she just wake up and wake him up and their son up 200+ years prior. I'm guessing since there was still power in the system it used that power to keep her and the son unconscious or something? Dunno. Author didn't seem to feel like going into that, likely cause MC doesn't have the expertise to figure it out.