We'll have to learn Japanese. He is probably talking about his techniques, etc . . . I tried to get it translated, but the copy of the video wants to translate from German on YouTube.
I know, I noticed that too. You can tell he is excited with his great talent and creation. There's whole series of these videos. They are amazing, although unfortunately I do not speak Japanese. Not yet anyway.
Oh yeah, it's time consuming all right, but a lot of fun, and I still find it very relaxing because it is not the nerve-wrecking pressure of a flawless paint job and model. These builds are very forgiving, and thus they are good for the nerves!