Hey Forest,
I am not fluent in Japanese (yet). I have been studying for several months. I learned Hiragana and Katakana in one or two months give or take, it was really fast and easy. Basically I practiced writing the entire Hiragana/Katakana alphabet over and over again, and used what I wrote as a chart to study. If you watch Japanese TV shows or read manga, any Japanese interest really, you can practice writing words in hiragana and katakana using the chart as a reference (like katana, wakizashi, anime characters, Japanese actors, etc). You will memorize the characters pretty quickly. Kanji is where it gets challenging, it may be easier to learn the spoken language than to learn kanji.
As for the spoken language, I have learned some but not really a whole lot. It's actually less difficult than it seems. It can take years to properly learn spoken Japanese and kanji, in my opinion. Usable Japanese though? Not really that difficult to learn.