My situation is similar to the poster here: http://www.nihongoperapera.com/node/57

I am Japanese but I grew up with an almost non-existent comprehension of my mother tongue. Because I was exposed to Japanese on and off at a young age, I retained some receptive bilingualism in that I can seemingly understand some spoken Japanese.

Also, under certain circumstances I can rapidly achieve some oral fluency, but there is no structure to what I already know of the Japanese language. In other words, some parts of the language already come naturally (and are basically completely internalized) while other parts are merely mechanically understood (and I fear, at risk of atrophying away unless I take steps to seriously learn Japanese).

For example I learned hiragana when I was young, so when I try to read a sentence, the hiragana will read easily, naturally. But katakana, which I learned when I was older, reads more artificially for me. As if my neurons are still forming synaptic connections while I am reading. Kanji is, peh, for all intents and purposes I know no Kanji. I tried learning the Joyo Kanji out of Tuttle's "A Guide to Reading & Writing Japanese"; I made it up to the 80th character I believe but then could not study the characters regularly so I forgot them.

Also, with regards to speaking, I have a basic understanding of what 'sounds' right (this is how I know to organize my attempts at speech into Subject Object Verb) but this intuition falters quite a bit.

Apologies for the soliloquy above, but I wrote it to put into perspective what I feel I need now in order to learn the language.

1) A long-term outlook on what I will/should do. Languages have a reading, speaking and writing component. It seems like the reading and writing go hand in hand, but it is a vicious cycle with japanese because of the immense number of chinese characters you need to know. What should I focus on first? Writing? Reading? Speaking?

The reason I ask is because in the review of "Remembering the Kanji," it is suggested that the method may be useless because Heisig's style attempts to teach the characters without correlating them to some practical use--such correlation being necessary for a student to feel like he/she is "progressing." But, could Heisig's style be better for someone in my position with some hashed out rudimentary understanding of writing, reading and speaking?

2) I am interested in what kaeru thinks about the critical period hypothesis and how it impacts language learning. The critical period hypothesis was made with regards to learning your first language, but some aspects of the CP hypothesis have been carried over to second language learning. In particular, that if you attempt to learn a second language after a critical period (i.e. after puberty) that your brain chemistry will have changed in such a way as to compromise efficient language learning. The most apparent consequence being that adults who attempt to learn a second language rarely make it to native level (of course, some do, just not many).

Do you find that this is the case? What suggestions do you have for an adult learner to increase his chances at reaching fluency. (After all, it is supposed to be my mother tongue, and my motivation for wanting to learn it now is a sense of incompleteness not being able to speak Japanese fluently).

Thank you for your time.