BUSHIROAD MEDIA announced the release of the a free BanG Dream! online manga in Japan. You can read it via the LINE and the first issue already released on April 1, 2017. You can read the new chapters every Saturday.
You can find it on the following link but you can visit it only from Japan: https://manga.line.me/product/periodic?id=000094zi

The comic version BanG Dream! Bundle already released in Japan for 630 Yen (with tax). In this comic you can read a new chapter of the story, you will find an extra card for the smartphone game and you can read the latest information about the upcoming CD.