Moving to japan

I am japanese, well by blood. My mum decided to move to Japan, I am 15 and so I have to apply for highschool there. My mum says its very unlikeley because its not compulsory education although Japans prime minister has tried to make schooling more mullticultral// There is one place called kokusai but it is really hard to pass the entrance exam. I can talk fluently and know up to 3rd grade kanji, hiragana & katakana. No I am not a returnee// my mum wont pay for an international or private school and an exchange program won't accept me because I'm japanese and also because its to expensive so I think I have to work.
Any Ideas on what to do
Any job ideas for foreigners/ that will hire at fifteen

High school is not compulsory in Japan, however anyone who wants to go can do so and there are many options for low income students as well. Check with the city hall or ward office where you will move to. They should be able to help you out with information.

I am japanese, well by blood.

So you are Japanese, with a Japanese passport?

Any job ideas for foreigners

So you are a foreigner with a gaijin card?

Which one are you?

It's possible to be both, for example if their parent is Japanese but they were never registered in Japan. It would be helpful to know what your exact situation is though as it could have implications with your plans.

My mum is a japanese citizen & was a permanent resident//