I'd definitely recommend this game for people who want to expand their vocabulary, but there are a few things I'd like to point out.
-While this is almost never required for romance languages, in Japanese, Chinese and Korean, words, Especially adjectives and verbs, can be synonymous but imply different things. This is almost always the case in Japanese, where verbs have transitive and intransitive forms, but this is not listed in the definition, only one form is presented. This means doing research on the word you'll find yourself using more will help you be more fluent in the long run.
-So much katakana... I'd like to see really rare kanji forms of words, as they can appear in stories and some videogames (You know, like English games using the words, 'Thee', 'Thou', etc. They're rare because of their age, but they can still find a use in medieval style games!). In fact, I might prefer it that way as I want to learn as much words as possible and converting English to katakana is easy when you learn about how Japanese pronunciation works. Just add a note to say it's rare to avoid confusion.
-Some objects are... Odd. I saw this red box and the definition said it was a piggy bank or something, I was confused until I saw a dial, which meant it was a safe. Maybe you should make objects cliched/stereotyped and exaggerated to help people understand with a quick glance.
-It doesn't follow spaced repitition, so you can mash the replay button endlessly until you get yourself a star. If you're a serious learner, never press the replay button, as you just bring it back to your short term memory and fail to remember it the next few days, at least space the replays by an hour the *first* time you try it.
-Lists make it too easy sometimes, avoid using them and just use the random button, as I found myself just clicking whatever's next to the last object I clicked on, as I was able to remember the next thing I added right after. This is a mnemonic that relies on the location of the object INGAME, so it doesn't really help you learn. If you really want to do lists, run around the whole house clicking random items and adding them to the list, avoiding any sort of order or pattern.
And here's some tips for Japanese:
-Avoid Romaji, in fact, do kanji, when you don't know a word, you don't know it, there's no improving your ability to decipher meaning from kanji, so just dive right into it. Do kana if you're really keen on learning pronunciation before reading, and want to do it really, really quickly. Same thing probably applies with Pinyin and Hanzi, but I haven't played the Chinese version so I don't know if Pinyin is provided.
-The dots that appear between kana when you look at how to read the kanji is important, memorise the kana in sections divided by the dots, and their associated kanji (e.g. (毎日 [まい＊にち] まい is 毎 and にち is 日)) This is important, words might have multiple readings, and you might get them wrong, but if you memorise at least ONE reading for the kanji, you can type it on a computer, and even get the correct reading by typing the kanji on a dictionary.
-While katakana is easy when you know it well enough, sometimes it isn't, as you might say different versions of a word (E.g. Fairy Floss vs. Cotton Candy, (Well, it's neither when translated to Japanese, but you get my point!)) or it's just katakana but isn't based on English, (e.g. パン for bread). Either way, it's nice to learn a ton of katakana in this game as you get badges for it.
Other than that, it's good as you'll find objects in an every day home, and the exploration stops you from being bored quickly, and most importantly:
It makes you think of (and therefore associate the word you're learning with) objects and pictures, rather than the English translation, which means that you can achieve fluency which allows you to form sentences in the language you want in your head directly, rather than creating an English sentence, translating it to your wanted language, THEN saying, writing or expressing it.