I would say that the Japanese are the most "into" trains by a fairly wide margin. They permeate everyday life and popular culture there in a way which is hard to appreciate unless you actually go there. The Yamanote line is probably the most romanticised railway line in the world, appearing in countless shows, both animated and live action, and Shinjuku station is the most popular transport hub in the world, of any type, by far. It has over 200 exits (!) and is arguably the heart of Tokyo.
So yeah. Germans love trains, it's true. Japanese love trains and do so in that overboard way which is at once both cool and kind of scary...
Which begs the question, could train obsession be a substitute for not obsessing about military hardware?
On the other hand, I don't know enough about Japan, are they really obsessed about trains or do they just happen to be really really good at trains and use them a lot? They might be just pragmatic about them (quite the opposite of obsessed) and a high presence in daily life would naturally be reflected in pop culture.
So yeah. Germans love trains, it's true. Japanese love trains and do so in that overboard way which is at once both cool and kind of scary...