In the turbulent early twentieth century, following the Russo-Japanese War, a battle-hardened veteran known as Immortal Sugimoto discovers a desperate chance to change his fortunes. Saichi Sugimoto learns of a vast hoard of Ainu gold, a treasure hidden by a cunning criminal known only as Noppera-bo. Before being captured and imprisoned in the formidable Abashiri Prison, Noppera-bo tattooed a complex ciphered map onto the bodies of twenty-four convicts, who were then scattered across Hokkaido.

While panning for gold in the harsh northern wilderness, Sugimoto encounters a young Ainu girl named Asirpa. Her father was murdered by the same man who stole the gold, and she seeks the truth about his death. Together, they form an unlikely alliance, combining Sugimoto's ruthless combat skills with Asirpa's deep knowledge of the land and Ainu survival techniques to track down the tattooed prisoners and assemble the map.

They are not alone in this hunt. A dangerous three-way battle erupts as several factions converge on the treasure. The primary antagonist is Lieutenant Tsurumi, a charismatic but unhinged officer of the 7th Division of the Imperial Japanese Army. Tsurumi seeks the gold to fund a military coup to conquer Hokkaido on behalf of his war-weary soldiers. Opposing him is Toshizo Hijikata, the legendary and undefeated former vice-commander of the Shinsengumi, who was supposed to have died years ago. Hijikata has his own ambitions for the gold, adding a layer of historical weight to the conflict.

As the chase intensifies, the battle lines converge on the icy, inescapable fortress of Abashiri Prison, where the enigmatic Noppera-bo remains incarcerated. Believing the mastermind holds the final key to the puzzle, Sugimoto and Asirpa must infiltrate the prison, leading to the largest and most brutal confrontation in the series history. Surrounded by a sea of escaped convicts, ruthless military police, and rival treasure hunters, the hunt for the tattooed skins descends into a violent, three-sided free-for-all. Returning allies such as the cunning escape artist Yoshitake Shiraishi and the mysterious sniper Hyakunosuke Ogata are pulled into the fray, forcing every character to choose between loyalty and survival in the race to unlock the gold's secret.