GRND records when you sleep and how long you study, then turns the regularity of that rhythm into a score. Logging takes two taps. The aim is that you no longer need one app for sleep and another for study.
This app is not a medical device. The scores it shows are reference information to help you look back on your habits, and are not intended to diagnose, treat, or prevent any illness.
Note on language. The Japanese versions of these documents are authoritative. These English pages are provided for convenience; if the two differ, the Japanese text governs.