I may not be a native speaker, but it is indeed possible to learn just by yourself :) I passed until JLPT N2 (taking N1 this year) without having a teacher since the beginning, and people always told me before that it was impossible, but from my experience it's possible. The only drawback you'll probably get is your conversational skills, which was my problem since I didn't have anyone to talk to but I can read Japanese literature perfectly fine, and hence that was the reason I joined italki and other language exchange sites.

A native Japanese who also is learning other languages including Polish saying hi. I've been searching resources online for a while before I got ready, which means that it is sometime hard to find the way at the beginning, but still keep going. You shall be given...

I totally agree with Haruka-san. Good luck to you!

Thanks, Haruka. :) It improves my mood.

I think it is possible. I haven't got any teachers very long. My English has been improving more quickly since I started using the Internet. A language is a communication tool, so the Internet is the right one to use! I also think it is helpful to have a chat with native speakers though Skype, Line or whatever, especially when you are a beginner or pre-intermediate.