Today I found this Ultraman statue at Shinbashi station in the Yamanote line. Next to the statue there was a stand where you can get a stamp to certify that you have found the statue. It seems that it is a promotion to collect the Ultraman characters stamps. If you manage to get all the stamps you will be able to have a chance to get several prizes. These kind of marketing promotions are known in Japan as スタンプラリー (Stamp Rally). To participate in them you have to use the official passbook and then collect all the stamps.
More information about the stations and the places where you can collect the stamps