(Sorry, maxso216, but this is truly the shortest functional train line in Japan.)

The DisneySea Electric Railway is a 2-station line coming in at less than half a kilometer in total length (0.48km). Even at the relaxed 15kph speed of the trains, it only takes two and a half minutes to traverse the entire line. The line runs between the American Waterfront and Port Discovery areas of Tokyo DisneySea. It also has what must be the smallest fleet of rolling stock of any line in Japan; Four two-car sets, of which only two or three sets are in operation at any given time. (Fewer sets than even the Tokyo Disney Resort Line monorail.)

Sign over the American Waterfront Station entrance:

A trivial oddity about the trains is their numbering system. Which initially appears to not be a system at all. All eight cars of the four train sets have a unique (yet random) car number, and the set pairs are never separated from each other. The only discernible pattern with the car numbers is that the final digit in each number seems to represent in which order the sets were commissioned:

Set #1) 5591 & 1111
Set #2) 1022 & 2842
Set #3) 1783 & 5593
Set #4) 0214 & 4824

Set #1 traversing the elevated tracks over American Waterfront:

The origin of the train sets are a bit of mystery. Their manufacturer is not known. Since the beginning of operation in 2001, the DisneySea Electric Railway has been sponsored by Takara Tomy - A Japanese toy company that makes functioning toy train sets, including replicas of the trains on the DisneySea Electric Railway.

Set #3 passing another train bound for Port Discovery Station.

It is possible that the train sets were designed and built by WED themselves as simply another park attraction, or possibly by Kyosan Kogyo Co. Ltd. which manufactured the sets used on the Western River Railroad in Tokyo Disneyland. The DisneySea Electric Railway sets are modeled to resemble some of the elevated streetcars used in what became the New York City subway system at the turn of the 20th century.

Preserved Brooklyn Union streetcar at the New York City Transit Museum, Wikipedia

All four sets have been in service since Tokyo DisneySea opened on September 4th, 2001. Apart from having air conditioners installed in 2015, there have been no notable improvements to the trains themselves.

Set #3 leaving American Waterfront Station:

Is the DisneySea Electric Railway an actual train line? Yes. In addition to having two stops which allows the line to be used by park guests to easily get from one side of the park to the other, the line falls under the jurisdiction of Japan’s transit authority. Despite being on private land and requiring admission to the park to use, DisneySea Electric Railway must adhere to the same standards as any other public train line.

Set #2 arriving at Port Discovery Station:

When Tokyo Disneyland was built and opened in 1983, the Western River Railroad was purposefully designed to have only one stop and run in a loop that sent riders back to where they started to avoid a law that required charging a train fare and that a departure schedule be posted and followed by the line’s operators. This decision made it another attraction, rather than a functional line like the Disneyland Railroad in Anaheim. This particular law was abolished in 1987, allowing DisneySea Electric Railway to function as an actual line with destinations without needing to follow those rules.

(This is my first attempt at a long form post here, let me know how I did. All pictures are by me unless noted.)