As far as languages go, Japanese is structured a lot like a programming language. If you learn five or six "bunpo" or grammar rules, you can go a very long ways. Then, to improve, just add rules to your mastery.
When I first learn any programming language I start with basics: variable binding/assignment, types, conditionals, looping, etc. Japanese fits very nicely into the same learning method.
Does a language have if/then? is it 'if (<expression>) { expression }'? Or 'if <expression> then <expression> end if'? Is there an 'unless' form? What about 'else'?
For Japanese, it's <expression> naraba <expression>. That's it. Unless? <expression> nakeriba <expression>.
How about while? <expression> nagara <expression>
For people who can learn the gist of a programming language in a week, you could learn the gist of Japanese in a week or two. That doesn't mean you would be fluent. You'd still need to learn thousands of vocabulary words. But the basic mechanics can be mastered in days or weeks. More mechanics can be layered as needed.