This game is titled 'Oide yo Doubut su no Mori', or Animal Crossing Wild World to Western fans. This is indeed the Japanese version of the game, therefore all text and dialogue in the game are all written in Japanese.
I bought this game in Japanese after buying the English version 9 years prior, therefore I needed little knowledge of Japanese in order to play, as I already knew the basic plot of the game. The dialogue in the game in written in all three of the Japanese writing systems, Hiragana, Katakana and Kanji, therefore it would be beneficial to players if they knew both Hiragana and Katakana and some Kanji. Compared with New Leaf (Newest instalment in the Animal Crossing franchise), the Hiragana and Katakana characters are NOT displayed above the Kanji characters, so if you are unsure of what a certain Kanji sounds like, you just going to have to deal with it. What I did like about the typing in this game is that there is still an English keyboard if you press the [1/A] button on the typing screen. I think that you can only type in Hiragana and Katakana in the game, however there is a Kanji button, but you can't press it.
I bought this game with the knowledge that some game systems do not play games from another region, however, this game DOES play on PAL DS systems, meaning that even if you have the European DS console, you should still be able to play this game. This game however does NOT play on the 3DS console, despite it being able to play DS games, the 3DS console is 'region locked', therefore only allowing it to play games from its region, a PAL 3DS can only play PAL region games. If you put the cartridge into your DS and it does not work, simply turn off the DS, take the cartridge out, blow the cartridge and the game port in the console, and just fire it up again. Repeat this until it works.
So in short, this game does play on PAL/European/UK consoles, despite being a JAP game. You can type in English still, despite all dialogue being in Japanese. I think this game is really good, and it brings back the nostalgia of playing Wild World. You may want to consider buying it!