In 2012, Kinki Sharyō presented a DMU prototype with a hybrid powertrain. It was called “Smart BEST”, with the acronym standing for “Battery Engine Synergy Train”. The idea was that the diesel engine only had to provide its maximum power for short periods of time, so a smaller engine could be installed. Traction power always comes from the batteries, which are being recharged from the engine over time and from regenerative braking.

One half of the two-car unit contains the batteries, the power converters and four traction motors with a total of 600 kW. The other car contains a 302 kW diesel engine and other equipment. The batteries allow for a continuous speed of 70 km/h, but 100 km/h can be reached for a short time. The train made test runs on several lines in 2012 and 2013 and was used as “Hello Kitty Wakayama” with a special livery on weekends in the year 2014. Although the Smart BEST doesn't have a direct successor, today there are more diesel hybrid trains in Japan and other countries.