Extremely poor quality and credibility of the JLPT content itself is questionable
Aside from the ridiculous amount of bugs making the app unusable in the long term, there are a lot of formatting issues with the reading-based questions, and the audio for the listening questions are sometimes wrong or unavailable altogether. Additionally, the vocabulary and grammar in each difficulty level do not accurately reflect the real test (at the N2 level, there are more N1 questions than there are N2). More incriminating, however, is the fact that there is no single-month payment option, and all the available subscriptions appear to be discounted permanently, which is extremely deceptive to customers. I cannot trust the developer as an app developer nor as an authority in JLPT testing. Please do not waste your hard-earned money on this app—there are much better, reliable JLPT resources online for free.