Donarto why do you want to come to Japan?
If it is to learn the language then study as much as you can before coming. Many people often say you dont need to know any Japanese when you come and I often here people say you dont need to learn it at all while being here. If you cant speak any Japanese it would be very hard and frustrating. These types of comments are usually from those who work in private english companies Eg: Nova. When I first came to Japan I was stuck in the `Nova environment`. I was living in a nova house with other Nova employees. Everything was Nova Nova. Nova has the reputation for being basically the worst company to work for. The money is good and a lot of the students are good too. But the company doesnt care about its employees. And I feel very sorry for the Japanese staff who have to work in that company.
There are heaps and heaps of different private english companies here.
I recommend trying to get a Job at a public school . Elementary, Junior High, High or even Uni.
Not only do you experience Japan to the fullest it is great for your study.
Ps: I have a similar degree