I want to move to Japan. Need Advice.

I am 20 years old (21 in July) and am trying to plan on relocating to Japan sometime in the next few years for a career. I am very serious about this goal. I have always loved Japanese culture and I have been to Japan twice within the last year (for 3 weeks in October and 1 month in February) and I am positive that this is what I want. I will be starting college this September (in the USA) for my first year. However, I am not sure what I will study. I am thinking maybe either a biology major or a major involving computers. After about 2 years in the US, I hope to study in Japan.

My question is, what careers would be better for me to find a job in Japan? Would I find more luck in a biology field or a computer field as a foreigner in Japan? If neither of these are good, what other fields or careers should I be looking into? My interests and strengths are in computers, the sciences, and working with people.

Because I am only 20, I have the time to plan ahead before I go. So besides college and getting better with my Japanese, what else should I be doing or looking into to help me prepare for this?

Any input and advice would be greatly appreciated. Thank you!

Learn Japanese.
Then get a degree in the medical field such as psychology/ psychiatry. Or nurse aid, specially for seniors.
Good luck!