In 2008, in preparation for our first child, we moved to the biggest apartment we ever lived in in Japan. It had the glorious name Chunichi Mansion Chiyoda. And it certainly was a “mansion” as far as we were concerned. We had a living room/dining room, a bedroom, a room for the baby and I even had an office! In Japan this is known as a 3LDK (3 room, living room, dining room, kitchen). Below is a short video walkthrough on the day we left it (hence why there is no furniture). This will give you a sense of the size.
https://www.youtube.com/watch?v=jQUUQc_bWog
The layout is slightly different, but here is a comparable floor map (just swap the tatami mat room on the western side with the “Western” room on the right):
Now, what is the actual size of this mansion? It was about 57m² which is roughly 613ft². What an efficient use of space! We felt like we had tons of room. I barely used my office (it turned into basically a storage room), and we hosted parties and guests stayed over often.
Currently in Canada we live in a 2 bedroom house that is more than 1000ft². We already don’t use the living room, which takes up a quarter of the house. We could easily move into a 600ft² space again — if there were any that were built with such space efficiency as in Japan. I wish I could transplant my Japanese mansion here.