Shinpachi Nagakura appears as an elderly man with a bald head, full beard, and visible wrinkles, contrasting his younger depiction featuring dark, parted hair and a beard but no wrinkles. Born in Musashi Province, modern-day Tokyo, he trained at the Shieikan dojo in his youth, befriending Toshizō Hijikata. His reckless and violent temperament earned him the nickname "Gamushin." He joined the Shinsengumi alongside Hijikata and Isami Kondō but frequently clashed with Kondō over his playboy behavior, requiring Hijikata's frequent defense. Following the Shinsengumi's scattering during the Battle of Toba-Fushimi in the Keiō era's fourth year (Meiji 1), Nagakura refused to rejoin in Edo due to his dislike of Kondō, parting ways on hostile terms with both Kondō and Hijikata. Later, Nagakura served as a swordsmanship instructor for the guards at Kabato Prison, conducting annual short training sessions. This role earned him significant trust from prison authorities, allowing him to make requests. During one session, he encountered Hijikata among newly arrived prisoners, who recognized him by his old nickname "Gamushin." Nagakura confronted Warden Shirosuke Inudou about not being informed of Hijikata's incarceration; Inudou refused access due to personal hatred stemming from his brother's death. After threatening Inudou, guards ejected Nagakura, but he later gained permission to speak with Hijikata through the chief guard. Their conversation revealed unresolved tensions from their past fallout, though Hijikata dismissed Nagakura's self-reproach with a smile. In Otaru, Hijikata and Tatsuma Ushiyama visited Nagakura, who supplied them with a base of operations, capital, and foreign-made firearms. Nagakura expressed reluctance to join Hijikata's war plans, citing his age and stating, "If a man does not die when he is meant to, what awaits him is a shame worse than death." He speculated whether Hijikata sought a place to die, which Hijikata denied. Ushiyama identified Nagakura as the Shinsengumi's best swordsman and deduced their pursuit involved more than gold. Nagakura traveled with Hijikata's group to Yubari, confronting Saichi Sugimoto's group over tattooed skins. He urged Sugimoto to sell the skins and return to a quiet life, but Sugimoto refused. Dining together, Nagakura listened as Sugimoto provoked Hyakunosuke Ogata. After Ienaga suggested Chouan Kumagishi could identify forged skins, Nagakura accompanied Kiroranke and Yoshitake Shiraishi to search mines for a uniformed corpse; miners reported no such discovery. Utilizing his Kabato Prison connections, Nagakura arranged a meeting with Kumagishi, only to learn from Warden Matasuke Ooshima that Kumagishi died during an escape attempt. The group then planned to move to Abashiri Prison. When the 7th Division captured Shiraishi, Nagakura relayed townsfolk reports about the soldiers' movements and expressed doubt about Shiraishi's ability to escape quickly. After Hijikata's failed rescue attempt, Nagakura advocated leaving Shiraishi behind since they possessed a copy of his tattoo, though Sugimoto insisted on a rescue using Kiyohiro Suzukawa's con artist skills. At Abashiri Prison, Hijikata showed Nagakura and Ushiyama an item belonging to tattooed convict Shinzou Doi. In Kushiro, an Ainu man named Kirawus identified the item as part of a tufted puffin, aiding their search. Nagakura is characterized by pragmatism and combat-focused dialogue, declaring, "Once the fire starts burning inside me, only your blood will put it out." His swordsmanship, hailed as the Shinsengumi's finest, remains a core skill. He shares an age with Ienaga and stands approximately 160 cm tall.