With Japanese, there is no learning "quickly". If you want it to be on the "easier" side (and it still won't be easy), you won't be getting it for free, either, unless you pirate something. I use Rosetta Stone and it's slow process BUT it is the "easiest" (and sometimes fun) way I have yet encountered for learning Japanese. There is a LOT of repetition but that is what really cements it into your mind. That and the fact that it doesn't just have "this word means this". It has pictures and you figure it out for yourself through a bunch of exercises. It really sticks in your head a lot better and it starts out simply so you can get into it. I haven't studied in a long time because I did too much in too short of a time and burned myself out. I'm not sure I'm even learning anything anymore so I think I might go back a few lessons and start over again. I do wish there was a glossary or something for a quick reminder of what a word means, though.