how about part time job for for foreigners
You will find it very difficult to get a job if you do not understand Japanese. For most part-time jobs the ability to speak fluently is more important than the ability to read or write fluently, but you won't have that ability before you go to Japan, and not even after a year of being in Japan. You won't earn a lot from these jobs, provided you can get any anyway. It is still very rare to see foreigners working in Japan outside of jobs connected with teaching English.
But you should know that in order for the Japanese government to accept your request to study abroad there you must prove to them you have enough money to live in Japan *prior* to entering. This means showing either you or your parent's bank statements to show you have the money to afford to live in Japan. They won't accept any statements of "I plan to work to earn my way.