"Bakumatsu Rock" is set in an alternate version of Japan during the Bakumatsu period, where the Tokugawa shogunate enforces strict control over society through the use of "Heaven's Songs"—music imbued with divine power that suppresses individuality and free thought. The shogunate, led by the authoritarian figurehead Iesada Tokugawa, uses these songs to maintain order and eliminate dissent. Music has become a tool of oppression, and any form of rebellious expression is swiftly crushed.

The protagonist, Sakamoto Ryoma, is a passionate and free-spirited young man who dreams of revolutionizing Japan through rock music. Disillusioned by the shogunate's control, Ryoma forms a band called "The Iron Heaven" with three other talented musicians: Kogoro Katsura, a skilled guitarist with a calm demeanor; Shinsaku Takasugi, a fiery and rebellious bassist; and Takechi Hanpeita, a reserved yet determined drummer. Together, they aim to challenge the shogunate's monopoly on music by performing their own rock songs, which inspire hope and rebellion among the oppressed populace.

As the band gains popularity, they attract the attention of the shogunate's enforcers, particularly the elite group known as the Shinsengumi, who are tasked with eliminating any threats to the regime. The series explores the clash between the band's revolutionary ideals and the shogunate's authoritarian rule, with each performance by The Iron Heaven serving as an act of defiance. The narrative delves into themes of freedom, resistance, and the transformative power of music, as Ryoma and his friends strive to awaken the people of Japan to the possibility of a brighter future.

The characters are deeply intertwined with historical figures from the Bakumatsu period, though their personalities and roles are reimagined to fit the series' unique premise. Ryoma's unwavering determination and charisma drive the group forward, while Kogoro, Shinsaku, and Takechi each contribute their own strengths and struggles to the band's dynamic. The series balances its historical inspiration with a modern twist, blending traditional Japanese elements with the energy and aesthetics of rock music.

Throughout the story, The Iron Heaven faces numerous challenges, including internal conflicts, external threats, and the moral dilemmas of their rebellion. Their journey is marked by both triumphs and setbacks, as they navigate the complexities of their mission to liberate Japan through music. The series culminates in a climactic confrontation between the band and the shogunate, highlighting the enduring struggle for freedom and the enduring power of artistic expression.