[Matsun]

Hello:
I'm Mark, 18 years old and from Germany. I am - well actually I was a student visiting 12th grade here till everything broke apart with my family here 2 months ago. I don't want to go into details, all I can say is that my Grandpa passed away resulting in greedy heirs (including my father) fighting for the left-over heritage. Quarrels between my parents finally resulted "surprisingly"(wasn't going well anyway since last year...) in divorce. Well I don't want to bother you with this, to cut a long story short, the reason I came here is the following:
My mother suggested that I visit and live at my relatives in Japan for a while to cut off some stress.
Result: They approved and my uncle ( german btw as his wife ) suggested visiting a Japanese Public High School while I am there.

First of I want to thank you all in advance, please answer my questions:
My questions to you Experts: I know more or less that you only are able to get a visa for max. 1 year, to stay in Japan, is this right? Will I actually be able to go to High School there? If it is possible to stay more than a year, can I graduate if I manage to get through High School? And my last question, are Public High Schools in Japan tuition free?

Thanks in advance,
Mark.