Gishirō Tsukamoto is the primary antagonist in the story of Lady Snowblood, serving as the leader of the group of four bandits who attack the family of Sayo Kashima. He is responsible for murdering her husband and young son before participating in the rape and torture of Sayo herself, an act that sets the entire generational revenge plot into motion. Following these initial crimes, Tsukamoto continues his life of villainy, eventually rising in status by engaging in large-scale illegal enterprises. He becomes a wealthy and powerful smuggler, dealing in opium and weapons, and uses his fortune to build connections that help him expand the Japanese empire. To escape the police who are searching for him due to his opium smuggling, he successfully fakes his own death in a shipwreck, allowing him to continue his criminal operations from the shadows.

As a character, Gishirō Tsukamoto embodies ruthless ambition and a complete lack of moral restraint. When confronted with the consequences of his past, he dismisses them outright, stating that he has no time for "twenty year old vendettas" as he is more focused on profiting from an impending war. His cunning is matched by his cruelty; upon learning that Yuki is hunting him and has befriended his estranged son, Ryūrei Ashio, he does not hesitate to use his own child as a pawn. He subjects Ryūrei to torture in an attempt to lure Yuki into a trap and ultimately murders his son when the young man tries to protect her. He also kills one of his former allies to cover his tracks and is willing to use his own followers as human shields.

In the narrative, Tsukamoto represents the final and most significant target of Yuki’s vengeance. His role is to serve as the primary obstacle in her quest, the mastermind whom she has been hunting since the beginning. He is the last of the four original criminals to be confronted by Yuki. The conflict with him brings the story to its climax, forcing Yuki to confront a man who has adapted to the changing times of the Meiji era, becoming a wealthy merchant dealing in modern weaponry. His key relationships are defined by exploitation and abuse. His connection to his son, Ryūrei, is one of abandonment and manipulation; he has not seen his son for a decade and shows no paternal affection, only using him as a tool. His relationship with Yuki is purely adversarial, built on the legacy of his original crimes and her single-minded purpose of retribution.

There is little development in the sense of a positive change. Instead, the character is revealed over time to be even more calculating and corrupt than he first appears, especially with the revelation that he faked his death. His end, however, is a significant narrative development. During a masquerade ball, Yuki finally kills him. In his final moments, he plummets from a balcony onto the dance floor and tries to grab hold of a Japanese flag, dying as his blood seeps into it. This death scene serves as a symbolic condemnation of the new, Western-influenced, and imperialist Japan he came to represent. As for notable abilities, Gishirō Tsukamoto does not rely on martial prowess. His skills are those of a master strategist and criminal. He is highly intelligent, capable of orchestrating elaborate schemes, including faking his own death and evading the law for decades. His power comes from his wealth, his network of thugs and informants, and his willingness to use modern technology, such as an automatic pistol, to protect himself.