You are looking for a governmental scholarship called the Monbusho scholarship. This is offered to students, usually with some proficiency in Japanese, in a variety of specialities: cultural studies, language arts, engineering, sciences.
They are intended to expose the Japanese students at the universities to those pursuing similar interests from countries outside of Japan’s typical sphere of influence.
There are a variety of lengths and values for these types of scholarships…some include language training and subsidized living accomodations, sometimes in Japanese dormitories sometimes in segregated dormitories….don’t ask why they would want segregation, but, you may learn more about that when you are actually studying….Monbusho, from the Ministry of Education,
What can I contribute to Japan as a scholarship holder?
Do you mean staying in Japan after you finished your degree, or just contributing while you are studying as an international student?
Most Colleges have something like “International Students Club”, and they welcome European / North American to share their life experiences. You may also work as an English tutor.
Japan usually does expect their international students go back to their home country after they finished the degree. You may share your love on Japanese culture with your community, and the Japanese Embassy is very willing to help you in this matter.