Mikuni Motor Co., Ltd., Osaka, 1955
Mikuni Motors (which I don't think is the same company as the Mikuni carburettor one) is listed as making two machines. One called the Road Hero (ロードヒーロー号) and the other shown here called the My Car (マイカー号). The My Car was a three speed, four stroke OHV 250cc machine with plunger rear suspension. Possibly a one year only company.