I started learning Japanese about 3 years ago, and I don't think I started off very well...
So hopefully I'll be able to give you advice based on my mistakes?
Probably the most important thing is learning hiragana and katakan first. You won't get anywhere if you can't at least read those. It takes a day to learn each. Don't do "one kana a day" or whatever. Just get it over with in 2 days and then youre set. Do hiragana first, then katakana. While you're learning those, you'll learn the pronounciation of them. obviously your pronounciation wont be perfect at first, however if you listen to japanese music or people speaking japanese, it's very easy to pick up.
Then i suggest buying a book to start on basic phrases/vocab/grammar. I would suggest starting with "Genki I". I used this book, and out of all the (beginner) books ive bought, this one has been the best... and i have a lot of books. its totally worth it, and then you can move onto genki II afterwards.
then as you gradually learn some grammar and vocabulary, you can start kanji.
also, i would suggest learn a bit about japanese culture, if you dont know anything. its important to know if youre going to go to japan, and its also very connected to the language; for example,. how you should speak to someone (formal?, informal?, honorific?) Although you might know some of this already being that you're partly japanese.
Anyways, good luck on your journey to learning japanese