You may well have read some fanfic in which Ranma is fighting someone on the top of a train in Nerima (or almost anywhere in Tokyo, for that matter). It'll be safe to say that the author assumed Tokyo's trains to be diesels. Wrong. Most of them are electrics fed 1500V DC via overhead catenaries. The Shinkansen trains, I believe, are the main exception, as they need a 25kV AC feed.
Very likely there are other 'too-too impossible' things about.