His videos are quite famous - that one has over a million views.
I like this mod because I just recently rode the Narita Express and this is exactly the set up they use. The two trains are coupled from Narita airport to Tokyo station. Then at Tokyo they decouple and the two trains take separate routes to different destinations. Passengers stay on the train while this happens and would have been assigned a seat in a car on the correct train that is going to their station.
In his video I am amazed how well his trains run with so many cars on them. I wonder if he mods the engines to get more power.
Tons of content from this YouTuber and through the years he has purchased literally tons of used items from the re-sale shops in Japan. I like how he replicates entire train stations and routes on his floor of the real thing trains running in Japan.