I am actually learning Japanese and I've gotten pretty good in about two years. I would honestly be fluent if I wasn't a lazy and retarded piece of shit.
For an idea of my level, I can read most Manga and a lot of fantasy works. I can also watch and understand most anime, but I miss key plot points if there is vocab I don't understand (like some of the technical terms in Death Note).
I wouldn't recommend doing normal vocab decks. It's easy to just do Sentence Flashcards. You don't even need to study grammar is you constantly do a Sentence Deck.
I also used Rikasama with Firefox so I could easily hover over Kanji and get the translation. Now I actually have a Japanese Dictionary definition pop up instead of an English one.
Watching anime is also a good tool. Just turn off the subtitles since those are cope.
I wouldn't recommend using grammar guides or anything. They're too slow. I used some "Learning Japanese with manga" book, but it was super gay and I got bored.
I want to so I can read their porn without it being translated
This is why I learned and it's honestly the greatest decision I ever made.
Just jerked off to this doujinshi yesterday that was just released. No need to wait for (usually shitty) translations. There are tons of fetish material untranslated too, which is good if you're a degenerate like me.
Go to exhentai or whatever site you use, and just marvel at how much is untranslated. There is tons of good stuff in there that will never be translated. That alone is worth learning Japanese.
