It was an android version Kimetsu no Yaiba quiz. Only problems with a high degree of difficulty, such as problems that do not understand unless you read the manga well. After solving the quiz, you will be able to watch the anime and manga again. Think about the answer, so it's perfect for brain training, so let's have fun while doing brain training. At first, the number of quizzes is small, but later the number of quizzes increases and it is designed to keep you from getting bored. First of all, download it for free and enjoy it.