japanese is a "building block" language, so once you know a few words it gets easier to figure out words that incorporate the same blocks.
I see what you mean by building blocks. It's an agglutinative language
-- I've also heard it described as a mathematical language
in that there is a lot of order to it and by learning the basics, you can build up to the more advanced stuff. But the thing is, it just keeps on building up! I also agree that it usually continues to be a hard language if your own native language is radically different. The order helps, so you get better at certain things, but there are always more things…
If you find a language interesting though, you'll enjoy learning it.
With regards to aikido, it's the language of the founder and his disciples, the language of the country from which aikido originated and the language of the art's terminology. I don't think it's essential
to learn Japanese to learn aikido, but anything which reduces barriers between you and the thing you're trying to learn is going to help right?
By the way: we've just entered into the application period for the Japanese Language Proficiency Test
. I doubt I'll have time for study though…