Do a Google search. I will bet that you're going to need to pass a fairly high level of Japanese language tests for most universities. The high school and tech schools here show a pretty pitiful motivation and success towards learning English, if that's any indication. So, whether it's the entrance exam (most seem to have their own, testing you in core subjects as well as in the language), or all of your courses being taught in Japanese, bear that in mind.
Examples:
Center for International Exchange, Saitama University
Computer Science and Engineering | Kyoto Sangyo University | JPSS for international students
Computer Science | Tokyo University of Technology | JPSS for international students
You'll need to prove you can pay all tuition, too, in order to get the student visa.
My biggest concern is that you've apparently decided to spend your entire life here based on some Internet moments with a J girl. Pretty scary conclusion to draw.