I am not sure if this can help, but check this out -> http://www.studyjapan.go.jp/en/  It has information about student scholarships to study in Japan. 

I've seen several foreign at this school.

It's a very famous school.

But, I don't know if they support for visa.

http://www.kodokan.org/index.html

I'm not sure about it detail. Why don't you check HP of the embassy in your country or Judo federation something like that. I have heard an example of an entertainer in Japan, named So Takei,he got a scholarship of international golf organization and had been to the U.S. for 4 years. So,if you keep to search the Internet,you may find some support to learn judo. 

I'm afraid you are not allowd to stay in Japan with such kind of visa, to avert unauthorized labor.

THANK YOU SIR  SUGGEST ANY OTHER KARATE SCHOOL WHICH CAN SUPPORT VISA