The 400 Series Shinkansen trainsets were introduced in 1992 for Japan's newest Shinkansen high-speed rail links at the time, the Tohuku Shinkansen and Yamagata Shinkansen lines, collectively called the 'mini Shinkansen', since they feature large portions that were not newly purpose built Shinkansen lines but rather existing lines regauged to standard gauge and upgraded, to provide a cheaper solution than a massively expensive dedicated Shinkansen line built from scratch.

Clearances are much reduced compared to previous Shinkansen lines, and thus the 400 series units are much narrower than previous Shinkansen trains. Seat pitch is also reduced, which should be a warning to larger Westerners venturing to Japan!

Styling wise, the 400 series is another to have an aircraft-style nose with a pointed nosecone, though lower than 0/100/200 Series. Originally they were painted a medium silver grey with a darker roof and area around the cab windows and underframe, but they have been recently repainted, with a higher area of dark bluish-grey on the underside, coming up almost to the side windows, and separated from the silver grey with a green stripe. The dark grey on the roof and around the cab windows is gone.

They were originally six car sets, but a seventh car was added to each to reflect increased popularity of these services.