The Kokujou was first seen making an appearance at a tunnel in Shitori Station. On board was Biba, a son of the current Shogun. Other known passengers are the Hunters, an independent force that eliminates the Kabane.
The Kokujou looks almost like a steam locomotive. It is made almost entirely of heavy metal components. It is possible that a master key is required to operate the Kokujou, which can be inserted in a keyhole in the crew compartment.
The locomotive has a unique purplish brown color, with 2 headlights on each side.
It is possible that the locomotive cab is located at the very front of the locomotive. However, more information is needed, and will be revised when Episode 8 (or later) is released.
The locomotive is probably capable of running at very high speeds as opposed to ordinary steam locomotives, since it's engines have high output due to efficient vapor compression.
Its is similarly designed with the Fusoujou.
The appearance looks similar to a 4-8-8-4 steam locomotive. It has 4 wheel leading trucks, with two sets of 8 driving wheels per side, and a 4-wheel trailing truck. One Locomotive well known for this wheel arrangement is the Union Pacific #4014 aka "Big Boy".