Set up like a traditional JRPG, you go around the world, battle monsters, and try to rescue a princess. The story is simple and the graphics are just this side of terrible but Slime Forest Adventure is far more a vocabulary building tool than it is a game.
In battle, you type the phonetic reading or the meaning of the Japanese character you see above a monster's head to attack—much like Typing of the Dead. Each area you explore teaches one of the three Japanese alphabets: hiragana (sea), katakana (beaten cave), and kanji (forest). So it's great practice for those in their first year of Japanese study and beyond.
On the downside, Slime Forest Adventure is in no way a replacement for an actual Japanese class. As it has no sound, it does little to teach pronunciation and it teaches absolutely no grammar. But as a supplement to a class, it is excellent. You will quickly pick up hiragana and katakana and have far more fun playing Slime Forest Adventure than flipping kanji flash cards.
The free version of Slime Forest Adventure teaches hiragana, katakana, and the first 200 kanji and has different levels of difficulty tailored to how much Japanese you already know. The full version of the game teaches an additional 2,000 kanji as well as 3,000 common vocabulary words for $25 USD. Check out the video above to see it in action.
Slime Forest Adventure [Project LRNJ]