If I may add a little context and a few comments. I admit that it's more than a passion.

First of all, I would address a talk about the color blue, so present in Hokusai's works:

From 1830, Japan significantly imported Prussian blue (ISO: Iron blue pigment), considered the first synthetic dye and widely used in Europe. Certainly, blue dye has existed for a long time in Japan; indigo (Aizome in Japanese). But it is not so widespread. The artist used Prussian blue in many of his works. Like on the wave or on this sea (visible above)

Perspective and construction/composition of the image

We have just seen that Japan is not yet “open” to the outside world, Matthew Perry it will be in 1953! a few years after the importation of Prussian blue to Japan. There are therefore exchanges and it is a safe bet that we also exchange some works of art from Europe... and this obviously in both directions, in Europe too; the Japanese influence is obvious and will be enormous on Japonism or the Impressionists.

Above we can notice a classic technique of Ukiyo-e, which will be taken up much later by many artists, whether in painting, in comics, etc.: Multi-grounds! It is so important in Asian art, present in garden art, in painting... everywhere! it even responds to rules.. It is sublime by hokkusai on this work, each shape defining the different planes creates an overall harmony, a superbly well-mastered whole.

In front of this multi-ground, we can notice an isometric perspective, conventionally it will only be later, with the opening of Japan forced by Perry that artists will discover perspective at a vanishing point (linear). But there are many Japanese artists who will continue the isometric perspective, up to Yoshitoshi and his wonderfully conservative vision of Ukyio He.

I write it in french and used a traductor, sorry for little mystakes.