There is an entire community of Japanese vloggers devoted to the genre of tenbo shaso (展望車窓), which roughly translates as “train observation car videos.”
Basically, the vlogger, typically a trainspotter, sets up a video camera to look out a train window (車窓, or shaso, sometimes translated as syaso) and records the view for the entire journey.
There are two subgenres of tenbo shaso videos: “front view” (前面展望 , senmen tenbo) taken from the front of the train, and “window view” (車窓 , shaso / syaso) which records scenery as it passes by the passenger window.
Videos uploaded to YouTube typically run for at least a couple of hours, and are sometimes broken up into playlists to accommodate their long running time.
Viewers of these videos can, for example, take a trip right at the front of the train and under the shadow of Mount Fuji from Shizouoka Station to Tokyo Station .
The trip above was recorded in 2007 on the old Tokai (東海) limited express train , shortly before the service was discontinued a few months later.
If there is a train or tram line in Japan, there will be a shaso video of the entire journey uploaded on YouTube. For example, this playlist of 40 videos  records the entire train trip from Osaka to Sapporo on the northern island of Hokkaido:
It was recorded on the Twilight Express  overnight luxury train service which, until it was discontinued in March 2015 traveled from Osaka to Hokkaido up the rugged and rural Japan Sea coastline.
As Japan introduces more high-speed rail services, and thanks to cheap air travel and the increasing popularity of long distance highway buses, many long distance express train services are being discontinued.
The train videos thus often serve as a window into history while providing a sense of nostalgia for train buffs.
Popular Japanese train vlogger RailKingJP  has made dozens of train videos, often while traveling on business trips around Japan.
In this video, he shoots a “front view” video from the Yurikamome monorail  that provides service between Nihonbashi in Tokyo and the Odaiba waterfront development:
If you want to get an idea of what central Tokyo itself looks like, there are plenty of videos documenting the view from the Yamanote loop line that travels around the city:
These trainspotting videos are also a good way to observe how Japan continues to recover from the 2011 tsunami and earthquake  that devastated much of the long, isolated coastline stretching northeast of Tokyo.
Much of the rail line had been destroyed following the massive tsunami in March, 2011, and there were some doubts the railway would ever operate again. However, the rail bed has been rebuilt, bringing tourists back to the area.
How to Explore Japan By Train Without Ever Leaving Home
While there are thousands of YouTube videos that can let you explore almost every part of Japan by train from your own computer, it can be challenging to determine where to go if you don't read Japanese.
A good place to start is with the Wikipedia list of rail lines in Japan . Choose a rail line , and find the corresponding Japanese language page  to find out what the rail line is called in Japan.
In this case we were able to start from Wikipedia and find a video taken from the Chiba Monorail.