Play it again, Teruyuki. Now play it again.
What we have here is an interesting range of compositional techniques, not necessarily compositions. The pieces themselves tend to be fairly repetitive. Very repetitive actually. But there’s nothing inherently wrong with that; Philip Glass and company made their mark by playing the same damn thing over and over a million times, right?
So Nobuchika has here over a dozen little snippets of what would work as larger pieces if they were fleshed out and worked into different schemes. The amount of actual music here is rather scant once we remove all of the parts that are repeated, but the ideas behind them are interesting. For instance, several of the tracks implement certain studio effects such as reverb and delay on these very simple structures. Some of them have a very distant, faint voice in the background. I can’t make out what the voices are saying, not only because of the volume but because I would assume they are speaking in Japanese, Nobuchika’s native language. To be honest, this is an idea that gets old very quickly, as it is used by several pieces in a row. I understand that this is the nature of "ambient" music (i.e. it isn’t necessarily meant to be listened to and is supposed to serve more like emotional wallpaper in a way, which this does).
Another idea here is multi-tracking several pianos, which occurs on tracks like "Aquarelle". The problem is that it remains minimalistic, with each overdub only playing extremely simple, looped melodies. Imagine what you could do with several overdubs of virtuosic playing (the Romantics like Liszt or neoclassicists like Glenn Gould). Alas, we have to keep on imaginging because we don’t get the answer here.
The problem is that the mood remains relatively stable throughout the entirety of the album, as one of relative contentedness (a lone exception being "Requiem"). It is the soundtrack of daily life; pleasant, ordinary, simple. As such, it doesn’t really endure itself to one on any real emotional level but is simply something nice to listen to with a glass of wine, staring into a fireplace before going to sleep for the night.
Compositionally, it is, again, very simple. The closest analogue I can think of would be the series of "Gymnopedies" by Erik Satie (at least one of which I am sure you’ve heard at some point in your life); not unpleasant but not thrilling or deep either. Average.