in yotsuba&!miura's high raise apartment which yotsuba mistakes for house, in matter of fact she proclaim as a princess!!!!
chirs in sonic X lives in big fancy house, cause his parents are extremely rich and very busy, but loving parents.
you forgot to mention Cody Jones'penthouse apartment in teenage mutant ninja turtles 2003 fast forward, that's pretty much a big fancy house
in sailor moon you forget to meant hotaru tomoe's big fancy house in anime and manga and rei hino's big temple,and michelle and hakura's large empire house in anime and manga, and usagi tskino's two story house , her family is pretty well-off, and darien chiba's big fancy apartment, it stated that all sailor senshi are rich cause they live in rich section in tokyo!!!
in mnt gadien do you know that renior family is rich but doesn't live in big fancy house, just a nice house in N.Y.?!
BOYS OVER FLOWERS YOU DON'T ADD LIVES IN HUGE MANSIONS EXCEPT MAKINO WHO IS FROM POOR FAMILY!!!!!
Using big fancy houses to indicate social standing is a universal trope, not a Japanese thing. Still, the stuff on how it applies to Japan is interesting, and we have a ton of anime examples. Therefore, I'm moving the anime specific stuff to its own subpage.