Mishima Kodo Kogyo Co., Ltd, 1950-1954
This company still exists under the name Maruzen Industry Co., Ltd. making industrial machinery. Their web site includes a history of the founder and the motorcycles manufactured immediately post WWII. The Mishima story actually starts in 1935 when the company established a factory in Tokyo and after being bombed out in 1943 relocated to the distric of Mishima-shi where they continued to produce parts for the Nakajima airplane. At the end of hostilities the company was rebadged as the Mishima Machine Tool Works Limited Company in 1947 and made consumer goods such as sewing machines, while at the same time developing their first motorcycle. Engine manufacture was done in house as they had their own foundry.
Beginning in 1950, several models of machines were produced: Misima S (138cc, sloper), Misima M (sloper), Star (possibly QueenStar ?), Orion, 125cc Challenger and the Deer. The Deer was a bicycle clip on engine. All the engines appear to have been single cylinder, OHV 4 strokes.
Motorcycle sales started to struggle in 1953 coinciding with the ceasefire agreement in the Korean war. Engines were sold to other makes, however the motorcycle business was wrapped up in 1954 and the company renamed. The brand name appears to have continued to be sold for perhaps another 3 years being produced by another company (I haven't yet identified which company that was).