as rude as this is, your plan is ridiculous. I suggest you plan a proper career path for yourself; and draw manga as a hobby, you wouldn't make it as a pro, so forget about moving to Japan for the time being. If I may (since nobody give you any actual advice), I gave this suggestion to my brother who also want to become a mangaka.
I suggest that you do something along graphic designer, you still go to uni, you still do art and learn the fundamental, I don't know what it like in the graphic designer course, but if possible, spare an elective or two to do subject that focus on drawing people (only if the primary course doesn't include it). This way, you have a proper career for you and you might still want to pursue continue as a mangaka if you wish.

As for art and drawing manga, there very minor difference between western comic and manga. First obvious one is the face, and the other difference is the western comic character art tend to be a bit more blocky while Japanese art is more smooth.

So what does this mean? It mean that everything else is the same, so learn those. Drawing people (anatomy wise), drawing object, drawing scenery. If you look up the first chapter of Bleach and the latest one, it look like it was drawn by different people. There is no 5-easy-steps to become a managaka, there no university teaching you how to draw manga, it take time and practice. And don't just focus on the art alone; manga, comic, book, movie, they all serve a single purpose, telling you a story. No story, no manga. While you learning/practicing your art work, write up story, short one to help you putting your art into practice, practice your format to make a manga (or comic). Make one shot manga.