[Hatredcopter]

Here's another option to consider.

Attend a university in the US, but take a full academic year to study abroad in Japan. In most study abroad programs sponsored by a US university, all the credits you earn at a Japanese university will transfer back to your home university.

I did this myself. I went to a university here in the US, my first two years I spent in the US taking Japanese classes (among other classes related to my major). Then on my third year, I studied in Japan for a year. My Japanese improved drastically over that one year, enough so to be fluent in speaking. Right now I'm in the middle of applying to the JET Program, so I can work in Japan after I graduate this spring.

The big reason I recommend this option is because it truly is an extreme amount of work to go through in order to enter a Japanese university. And once you do get into a Japanese university, you're going to be dropped into an entirely new environment for four straight years. You may end up not liking it, and if that happens, all that work you put into getting in will have been wasted. You might think now that attending a Japanese university is the right thing for you, but unless you know exactly what its like, you could be setting yourself up for something you might end up not enjoying.

Studying abroad lets you go there for a year (or just one semester) and see how it is. A year of intensive Japanese courses in Japan is certainly enough to really get your Japanese language skills up to par. I also took part in an internship there at a Japanese law firm, and I had a chance to meet a lot of different people, and that can really open up doors (career-wise) for a person. Spoken fluency, an internship, and career contacts - all in one year - best choice I ever made, and I thoroughly enjoyed my time there.

Anyway... that's something to think about.

And also, I have to agree with MMM - complete literacy in Japanese in four years is a tall order to fill. You'll have to take some intensive, university-level classes for those four years, which is usually at least two hours a day, five days a week. If you can find those classes, afford those classes, and fit those classes around your high school schedule, you might have a shot. If there are no classes available where you're at, I personally don't think it would be possible to become 100% fluent in that amount of time.