I've just tried it (japanese).
May I suggest adding (optional) furigana for japanese? The problem with kanji is that you can't read a word you don't already know.
Edit: it seems like there's quite a bit of colloquial japanese, which is good (at least for me) . How did you build your corpus?
Edit(2): there are lots of bad single word translations (the underlined ones). They either change spontaneously between two fingerpresses, or are just plain wrong.
Also, I don't mean to be harsh, but I'm not sure what your app brings that duolingo and kitsun don't already do?
Edit: it seems like there's quite a bit of colloquial japanese, which is good (at least for me) . How did you build your corpus?
Edit(2): there are lots of bad single word translations (the underlined ones). They either change spontaneously between two fingerpresses, or are just plain wrong.
Also, I don't mean to be harsh, but I'm not sure what your app brings that duolingo and kitsun don't already do?