You will need Internet connection only at the time of downloading app and flashcard(s). You can keep using downloaded flashcard(s) without data connection.
Once you start the app, tap on the reload button at the top right corner. App will download flashcards by JLPT levels and topics.
Please try it. Also, do leave review on the Google Play Store.
The contents for this app are developed by Prachi sensei. Prachi conducts Japanese classes in Pune. You can view her profile here: http://zipvc.com/profiles/91-9604372267