Manjirō Tasukeya, who also goes by the alias Roman, is the main protagonist of Bakumatsu Gijinden Roman. He lives a double life in Kyoto during the late 19th century, a period of great social and political upheaval known as the Bakumatsu era. By day, he works as a helper, a jack of all trades who takes on various odd jobs for the people of the city, often for very little money. By night, he transforms into a phantom thief known as Roman, a retriever who steals back precious belongings that have been unjustly taken from the common people by corrupt officials and powerful conspirators. He is also referred to by the alias Nezumi Kozo during his nighttime activities.

Manjirōs background is rooted in a sense of justice and a desire to aid the helpless, though his methods are unorthodox. He is not particularly disciplined with money, often squandering whatever he earns on gambling, a habit that frustrates those close to him. He has a charismatic and somewhat roguish personality, approaching his work with a flair for the dramatic and a sense of showmanship. His motivations are deeply personal and moral rather than political; he is driven by a straightforward belief that taking from the powerful to return to the powerless is the right thing to do. He is also portrayed as having a romantic fascination with a famous courtesan named Okuni Taiyu, which adds a layer of personal desire to his character.

A key relationship in his life is with his younger sister, Koharu. She is aware of his secret identity as Roman and runs a decorative chopstick shop, often worrying about Manjirōs reckless behavior and his tendency to lose money. Her capture and subsequent brainwashing by the antagonist Admiral Perry become a major turning point in the story, forcing Manjirō to confront a conspiracy that threatens all of Japan. Other important relationships include his rivalry and eventual alliance with Magoichi Suzuki, a member of the Mimawarigumi, and his reliance on the inventor Gennai Hiraga, who provides gadgets and support for his heists. His network of friends, including the mysterious Okuni and various townspeople, forms the core of his support system.

Over the course of the series, Manjirō undergoes significant development. Initially presented as a carefree and somewhat irresponsible figure, he is forced to mature as he becomes entangled in a nationwide conspiracy involving foreign powers and corrupt factions within the shogunate. The kidnapping of his sister and the revelation of the larger plot push him to move beyond simple acts of thievery and take on a more heroic and self-sacrificing role. He experiences moments of despair and personal crisis, but ultimately finds the resolve to fight for the people he cares about and for the future of his country.

Manjirōs notable abilities lie in his exceptional skill as a thief and a fighter. He is highly agile, acrobatic, and proficient in hand-to-hand combat, often using unconventional tactics and gadgets. His resourcefulness and quick thinking allow him to infiltrate heavily guarded locations and outmaneuver his opponents. He is also a skilled swordsman, wielding a blade with confidence. Beyond physical prowess, he possesses a sharp wit and a talent for improvisation, which are just as crucial to his success as his combat skills. His dual identity as a humble helper by day and a legendary thief by night defines his role in the story as a champion of the common people against overwhelming injustice.