Despite the assumption that Masuda Method odds are increased by region of origin of a Pokemon, that is actually completely false. Masuda Method odds are increased by the language of the game you play, which is only changeable at the very beginning of the game.
So you can have two copies from the same region, (or one if you have HOME,) and as long as you picked two different languages at the start of the game, Pokemon traded between those games will be able to breed with the Masuda Method.
Masuda Method odds with Shiny Charm are 1/512 and odds without Shiny Charm are 1/683
Hope I could help, please ask if you have more questions!