Mini-Shinkansen is a concept of JR East to build Shinkansen tracks over the existing narrow gauge railway lines. The name comes from the fact that, while the tracks have been converted to the standard gauge used by regular Shinkansen trains, the loading gauge (which is the height and the width of the tunnels, bridges and other structures) remained the one used by the smaller narrow gauge trains. Thus, the Mini-Shinkansen trains are visibly narrower.
The first Mini-Shinkansen line was the Yamagata Shinkansen, and the second was the Akita Shinkansen, serviced today by the impressive E6 Series, photographed here in Tokyo Station. The train runs at full speed over the regular tracks (reaching 320 km/h) but only at 130 km/h over the converted Mini-Shinkansen tracks.
JR East, Shinkansen E6 series EXIF info:
Nikon Df
Lens: 24-70mm F/2.8G
Focal Length: 32mm
Aperture: F/5.6
Shutter Speed: 1/400s
ISO Sensitivity: ISO 1600