The Masuda Method applies when two Pokemon are from different language games. For example, if one Pokemon is from an American (English) game, and the other from a Japanese game, then it would apply.
It doesn't matter if one of the languages is your own or not. So a German Pokemon and a Japanese Pokemon would still activate Masuda because they are from different language games. However, two Japanese Pokemon breeding on an American game would not activate the Masude Method.