This is an official app for the game, and it is only for subscribers of the JJDSG YouTube channel. If you don't qualify for this, then the app is of no use to you. You can download it, and play the game with the names and characters of the videos that you are watching. The app allows you to register with your name, and the password that you have created for your channel. Once you have registered, you will receive a confirmation message. After that, you will receive the rewards. You will get a special gift for the daily giveaway, and a special reward for the monthly giveaway.