"Oi, Ryoma" is a historical manga that centers on the life of Sakamoto Ryoma, a pivotal figure in Japanese history during the Bakumatsu period. The narrative begins with Ryoma as a young, restless samurai disillusioned with the rigid feudal system of the Tokugawa shogunate. His journey unfolds as he transitions from a low-ranking samurai of the Tosa domain to a visionary leader advocating for modernization and political reform. The manga meticulously portrays his involvement in key historical events, including his role in the formation of the Kaientai, a maritime trading and naval organization, and his efforts to broker the Satsuma-Choshu Alliance, which was instrumental in overthrowing the shogunate.

The story delves into Ryoma's relationships with other prominent figures of the era, such as Nakaoka Shintaro, his close friend and fellow revolutionary, and Katsura Kogoro, a leader of the Choshu domain. These interactions highlight the complexities of alliances and rivalries during a time of intense political upheaval. The manga also explores Ryoma's personal struggles, including his internal conflict between loyalty to his domain and his broader vision for Japan's future. His eventual assassination, a historically significant event, is depicted with a focus on the impact of his death on the movement he helped to inspire.

Throughout the series, the narrative balances historical accuracy with dramatic storytelling, presenting Ryoma as a multifaceted character—idealistic yet pragmatic, courageous yet vulnerable. The manga captures the tension and uncertainty of the Bakumatsu period, emphasizing the sacrifices and risks taken by those who sought to reshape Japan. By focusing on Ryoma's life and legacy, "Oi, Ryoma" provides a compelling portrayal of a transformative era in Japanese history.