In April 2003, JR East, in partnership with the Railway Technical Research Institute, introduced the “New Energy Train” powered by a diesel hybrid system. It was based on the E127-100 class two-car EMU and was officially designated the KiYa E991. The single railcar with two driver's cabs combined a diesel engine with electric power transmission and lithium-ion batteries and was the world's first railcar with this type of drive. The findings from the tests were used to develop the two-car KiHa E200 hybrid multiple unit.
In 2006 it was converted into the KuMoYa E995, in which the diesel engine was replaced with a fuel cell. The diesel tank was replaced with six hydrogen tanks with a total capacity of 270 liters. In addition, the capacity of the batteries had been increased. The railcar was also tested in this form in daily operation in 2007, but there was no series production,
In 2009, the vehicle was rebuilt again, with larger batteries and a pantograph instead of the fuel cell. The batteries could be charged while driving via the overhead line and then up to 50 kilometers could be covered on non-electrified routes. At the time when test operations were conducted entirely on non-electrified lines, a stationary charging facility was built with a fixed conductor above the track. In this form, the vehicle formed the basis for the two-car EV-E301.