So they live in the mansion instead of having their own house? Is that a thing in Japan?
It's a giant mansion rather than a normal 3 bedroom house. They got room to spare and I'd argue that it's better for the children to live with the surrounding family/friends and friendly maids.
Rather than say it's a "Japan" thing, i'd attribute it more to a rich person thing as most rich kids inherent the mansion from their rich parents and so forth.
