The class 12, also called KuMoHa 12, is a collective name for similar electric railcars that were built between 1926 and 1941 for various areas of application. They were the first electric railcars used in Japan and operated on 1,500 volts DC. What they had in common was a length of around 17 meters, three passenger doors per side and benches arranged lengthways.

From the factory, the vehicles were power cars with one or two driver's cabs. With several conversions, the shape of many vehicles changed, so some temporarily lost the driver's cabs for use as powered trailers and got them back later. A total of 33 vehicles were transferred from the Japanese Government Railways to the Japanese National Railways in 1949. In 1987 the surviving vehicles went to JR East and JR Central where the last ones were retired in 1996 and 2002 respectively.

In order to be able to transport large numbers of people efficiently during the war, electric railcars that were simple and cheap to produce were developed. These vehicles, later named Class 63 by the JNR, were originally developed as power cars, trailers and driving trailers with the designations MoHa 63, SaHa 78 and KuHa 79. Their initial purpose was primarily to transport workers to the armaments industry. With four doors on each side, boarding and alighting passengers could be handled quickly, and thanks to an easy-to-manufacture steel car body, manufacturing could be sped up. They were the beginning of a long series of commuter railcars, which, with many doors and a high proportion of standing room, were able to cope with the immense number of passengers in the Japanese metropolitan areas.

Due to the course of the war, only relatively few examples were built before the end of the war. Immediately afterwards, production continued on a larger scale in order to cope with the sharp increase in passenger numbers. Kawasaki Heavy Industries now manufactured railcars with an aluminum car body, as this was now easier to obtain. These also featured luggage racks and upholstered seats. Of the 688 cars built in total, those built during the war wore out after just a few years because the manufacturing quality was very poor. The aluminum cars also had to combat corrosion, which could also lead to short circuits and fires. With the class 72, an improved derivative was created and ultimately almost all vehicles from the class 63 were converted to the class 72.

The poor manufacturing quality and high wear and tear of the class 63 meant that from 1952 the improved vehicles of the class 72 were built. For faster and cheaper production in wartime, some reinforcements in the body of the class 63 had been removed, which were now reinstalled. The electrical equipment has also been upgraded. The first examples still had the old traction motors, each with 128 kW, but new ones with 142 kW were soon installed.

490 class 72 vehicles were built ex works, which were either MoHa 73 motor control cars or MoHa 72 powered trailers. Between 1953 and 1955, a total of 667 class 63 vehicles, i.e. almost the entire stock, were converted to class 72 status. This resulted in the non-driven trailer KuHa 79 and the control car SaHa 78. Production and conversion measures were completed in 1958, and the successor, the class 101, had been in production since the previous year. The class 72 remained in service with passengers until 1985. Some vehicles were converted into postal vehicles that reached a maximum speed of 100 km/h.

The first modern Japanese electric multiple unit for local transport was the class 101, which was initially called “MoHa 90”. To improve acceleration and deceleration, all axles on all cars were each powered by a 100 kW traction motor, which could also be used for electrical braking. A total of 1,535 cars were built up to 1969, which were combined to form two- to ten-car trains. They formed the basis for other multiple units up until the 1980s. The last class 101 trains were used by the Chichibu Railway until 2014.

The EMUs of the 103 series were the direct development of the 101 series. Most of the carriages were powered, which now had 110 kW per axle instead of 100 kW compared to their predecessors. Some carriages were rebuilt directly from the 101 series. Over 3,000 vehicles of the original 103-0 series were produced and further series were created either by new construction or by refurbishing older vehicles.

They were used throughout Japan in commuter service and were generally made up of three to ten cars each. Since the beginning of the 21st century, a large number have been scrapped. Four four-car sets were sold to Indonesia, where they were used in the Jakarta area until 2016. In Japan today, only refurbished vehicles from JR West and JR Kyushu are still in use.

To create a cheaper alternative to the expensive class 201, JNR ordered the class 205 in the early eighties. To save costs, it didn't get a modern Thyristor control, but a conventional resistor control. Within ten years, a total of 1,461 vehicles have been built. They were combined to sets of two to eleven cars and were soon split between JR East and JR West. As usual, half of the cars in each set or even more are powered by four traction motors with 120 kW each.

For lines with the greatest passenger numbers, cars with six doors per side instead of four have been built. These have automatically lockable folding seats which allow an all-standing layout at rush hours. Starting in 2002, some sets have been refurbished with modern IGBT converters. After withdrawal by JR West and JR East, a total of 102 sets with 812 cars were sold to KAI in Indonesia. Additionally, some sets came to the private Fuji Kyuko in Japan.

The designations KiHa 30, 35 and 36 stand for diesel railcars built for JNR between 1961 and 1966. They are all four-axle cars with a license-built Cummins diesel and hydraulic transmission to both axles of one bogie. Their bodies measure 20 meters in length and they have gangway doors at the ends.

The most numerous type is the KiHa 35 with 258 built. It has a cab at one end and a toilet. The 49 cars of type KiHa 36 also have one cab, but no toilet. 106 KiHa 30 were built with two cabs and no toilet. This makes a total of 413 cars. While the two-car KiHa 30 are optimized for single running, the others were generally used in sets of two to six cars.

The state railway companies retired these cars by 2012 and replaced them with types like the KiHa E130. After this, some remained in service in Japan with private companies like Kanto Railway and Mizushima Rinkai Railway. Some cars had been sold to the Philippines. There they are mostly operated as two-car sets, sometimes hauled by a locomotive due to severe grades.

The KiHa 40 family railcars were built in larger numbers between 1977 and 1982 to replace various older commuter diesel railcars. A total of 888 vehicles of the three series were built, which differed primarily in the number of driver's cabs and the design of the doors. The KiHa 40 was developed for lower passenger volumes and is usually used as a single vehicle. That's why it has two cabs and narrow doors directly behind the cabs. The KiHa 47 is used in pairs and therefore has only one cab per car and double doors that are slightly offset to the middle of the car. The KiHa 48 also has only one cab, but narrow doors.

In addition, the sub-classes of the vehicles are designed for different climatic conditions. In the vehicles for the very cold climate on Hokkaido, for example, the entrance areas are separated from the seating area, while the windows in the vehicles for warm climates can be opened more generously. Likewise, the vehicles for cold climates have air suspension and those for warm climates have coil springs. The engine is a horizontally arranged six-cylinder turbo diesel, which was derived from the twelve-cylinder boxer of the KiHa 66 and delivers 220 hp continuously and 250 hp for short periods.

After the privatization and division of the JNR, the vehicles were distributed to all of the six successor organizations. Originally JR Hokkaido got 157, JR East 219, JR Tokai 59, JR West 257, JR Shikoku 53 and JR Kyushu 142 vehicles. In 2018, 714 units were still in use, some of which had been modernized and rebuilt. Some vehicles received 300 or 350 hp Cummins engines. Some vehicles are used today as “joyful trains” for charter excursions in special paintwork or with special equipment.