It seems you're living in Japan so you might know this, but even current land prices have risen considerably compared to 10 years ago (surprising!)

In some central Tokyo areas like Ebisu, while they don't match Shanghai or Hong Kong, land prices increased significantly for a period.

Also, as land is inherited from the parent generation, perhaps as a tax strategy, single-family homes on (relatively large for Japan) plots are being converted into condominiums and apartments, making the space per household increasingly smaller.