The story is set 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 offense. Ryōma Sakamoto and the other rockers rise up and change the world with rock 'n' roll for freedom and justice.


From the wikipedia page on the game this manga is based on.