Thanks for contributing @Asami-1! A first general comments regarding your PR:

In general we try to avoid introducing external images to the documentation, instead we prefer adding references to existing images from the example gallery. In this way people can access the code that generated a given image and reproduce it or play with variants of it.

My suggestion is then to either:

a) create a similar image within the narrative of the Kernel PCA example (maybe you can use this example as inspiration);

b) try to pass the same message as in the current state of this PR but using the images in this example without the need of reworking it.

A smaller remark: try to keep a maximum line lenght of 79 characters to follow the PEP 8 convention. That will make the work easier for the reviewers :)