First of all, this will be very hard. Japanese is quite different from pretty much any language you're likely to know, and not only do you want to learn it, but

First of all, this will be very hard. Japanese is quite different from pretty much any language you're likely to know, and not only do you want to learn it, but you want to do it without actually being able to practice speaking. That said, I learned passable Italian (again, similar to languages I already knew) through a combination of self-study and visiting the country. My advice would be to start directly with the hard stuff: studying the grammar rules and memorizing tables of word forms. Of course, the language is more than just the rules, but at least for me it worked fairly well to memorize the rules, internalize them, and then be able to use them in conversation. Hopefully, you've already learned a foreign language, so you know what this process entails. Most books tend to be oriented towards classroom study, so you have to look around in order to find that works well for self-study. Once you've learned enough to know how to use a dictionary, take a news article and translate it word for word. After about an hour, congratulations, you've just read and understood an article in Japanese. Now go back to studying grammar. Maybe using Google translate and looking at the Japanese text and the translation side by side would be just as good, but I worry it would become too easy to understand. Much later, once you can understand spoken text, watch movies with movies in Japanese with subtitles. Don't kid yourself and think you'll get much out of this if you haven't already built up a base of grammar and vocabulary, but it's useful for learning colloquial expression and for seeing immediately how the Japanese will phrase things differently from the subtitle language. Oh, and one other thing: learn the International Phonetic Alphabet. A book will try to guide you through the language's sounds by relating them to your native language, but this can be a crutch because sounds never match up quite right. Start following linkes from the Wikipedia page on Japanese phonology. It's a bit intimidating, but you can start with the sounds which are common to languages you already know and then come back to the more complicated ones later. As others here have observed, at some point, you need to communicate with actual native speakers. Maybe you can find someone in Japan who wants to learn Spanish (or English?) and you can exchange emails. And, of course, if you're serious, you should someday visit Japan, which will give you lots of opportunities to speak Japanese.