[Lonthego]

Many universities want to see that prospective foreign students have passed level 1 of the JLPT, which is around 1800 kanji I think and advanced grammar, but for whatever reason does not test speaking.

To be honest, I think it would be more beneficial if you went to university in the US, and did an exchange in Japan. I too once considered going to university in Japan, and was very close to doing it. The thing is though that US degrees are good almost everywhere, and Japanese degrees are really only good in Japan, and the quality of higher education in Japan save for a select few universities is actually on the poor side. University in Japan is basically a time for students to relax, because getting in is the hard part (the 'nyuushi' or entrance exams), and staying in requires little effort. Most students (and unfortunately their employers) care only about the name of the university they go to.

You need to be really honest about your Japanese skills here. Do you really think you could handle nuclear physics in Japanese? Speaking as an interpreter & translator who has studied the language for almost a decade, people don't just go from completing high school Japanese, to being able to read university textbooks about nuclear physics, or listening to professors lecture about it. I don't know your Japanese skills, maybe you could be a prodigy, or someone who grew up speaking the language, that's not for me to judge, but in any case you need to think long and hard about it: could four years of structured and systematic Japanese be of benefit for you? A US university could provide that. Or do you feel confident enough in your abilities to jump right into a Japanese university, knowing that people there won't be able to help you or explain grammar/words you do not understand? Also: do you think your interests could change? Most Japanese universities frown upon people changing their "majors", whereas most American students find themselves doing it at least once or twice in their undergraduate career.

I'm not trying to discourage you, I'm pretty sure I know how you feel..just wanting to get to Japan and live there..because that's how I felt too. And to that end I think a US university education and the opportunities it offers gave me a lot more tools to be able to do that than a Japanese university could. You can always study abroad during your undergraduate career, or go to post-grad Japanese universities that have a connection with your US university after you graduate. There are some amazing opportunities and programs that will let you live and study in Japan, all the while building up your skills and credentials that will let you live in Japan as long as you like when the time comes.