In the Bakumatsu era, at the end of the shoguns' rule over Japan in the middle of the 19th century: the Tokugawa shogunate uses the brainwashing Heaven's Songs by the top idols in Shinsengumi to subjugate the country and its people. In this Japan, writing or singing any songs besides the Heaven's Songs is a capital offence. Sakamoto Ryouma and the other rockers rise up and change the world with rock 'n' roll for freedom and justice. (source: ANN).
Guys, this is just how you image it. Totally unreasonable as music technique & lighting is way beyond the time of Bakumatsu, but everyone 'simple person' is in traditional clothing. There are fans, behaving just like they would today. Shinsengumi is half cop-half idol. The Rock of Ryouma is so powerful that it summoned his band-mates, and their song even creates fireworks... I have no words.
The rock - at last the first song - was not catchy enough to pick my interest, even though I find it quite funny how the studios try to keep up with the needs of fans, mixing crazy styles together.