I live in Tokyo. It's a complete myth that Tokyo is endless high-rises. I think you are confusing us with Hong Kong.
A quick search will tell you that around a third of Tokyoites live in houses, and around two-thirds in apartments.
We have a mixture of housing types.
There are townhouse type houses (technically detached, but they look like they are terraces from street level as the gaps bx houses are tiny); the old ones are typically two storeys, while new ones are usually three storeys to give more floor space. The majority are self-build, like in places such as Germany where there is a lot of self-build housing.
We also have apartment blocks of various sizes. We do have high-rises; I live in one myself. We also have a lot of mid-rise apartment blocks of four to eight-ish storeys, usually with elevators these days.
By the way, average floor space per person is now very slightly higher in Japan than it is in the UK, having risen consistently over the past 25 years or so. You might think that's population shrinkage, but not really. The population of Tokyo specifically has continued to rise throughout this period, and density of humans per square km has grown too, yet average floorspace per person is also higher in Tokyo than it used to be. That's because we've increasingly knocked down dumpy two-storey townhouses and replaced them with either taller townhouses that have three storeys, or with apartment blocks which means you are literally adding extra floor space.