The game is pretty good, in my opinion. I think it predates the anime too; there are lots of animes based on these games.
I don't know where to buy it, but for information on the PC game here's the getchu link:
http://www.getchu.com/soft.phtml?id=6320
and the official site link:
http://www.age-soft.co.jp/Product/Kimibo/index.htm
Since the game is 18+, these links are not safe for work.
There are also a number of walkthroughs available:
clicky
I like this one:
http://www.ct.sakura.ne.jp/~ko-ji/ga...ien/index.html
If you know a decent amount of Japanese, and maybe have a Kanji dictionary around, you can play through the game to the endings and know what's going on, at least with the walkthroughs. You might be able to manage without, but it'll be pretty difficult.
If you haven't tried a Japanese game before, and plan to, bookmark this page:
http://home.comcast.net/~kagamix2/xp-compatible/
Frank