[CaptainZapp]

I've only seen restaurants in exhibited historic Shinkansens.

Fret not. There is an on board service, which provides from ice cream over sakes and cold beers a variety of up to 3 bento boxes for sale directly at your seat.

The better option is to buy something on a train station, since the variety is much bigger.

Tokyo (station) is famous for the shop that sells ~ 200 different bentos from the whole country. A short stop makes a delightful train ride even more delightful.

The nice thing in Japan is that eating some fermented fish out of a bento box is completely acceptable, while yakking away on your cell phone is not (you can move out of the carriage if you must make a call).

As for timings. The most impressive for me was 85 minutes from Brussels to Paris, city to city. You must be pretty stupid to use a plane for that.