Tatsuma Sakamoto hailed from a wealthy Tosa Province merchant family. Though pacifistic, he joined the Joui War's final years as a key supplier, delivering weapons, capital, and resources to the samurai fighters. Fighting alongside Sakata Gintoki, Takasugi Shinsuke, and Katsura Kotarou, he earned recognition as one of the Joui forces' "Four Heavenly Kings." His formidable combat skills, particularly his swordsmanship, earned him the moniker "Dragon of the Katsurahama." A pivotal battlefield moment saw Sakamoto sustain a severe injury to his right arm while attempting to carry an injured enemy to safety. This injury caused permanent damage, ending his ability to wield a sword. Declared "already dead" as a samurai by Takasugi, Gintoki later encouraged him, stating a samurai's worth extended beyond swordfighting and that Sakamoto's war was "not some petty war you can clean up with a broken pole." After recovering, he found his comrades vanished. He eventually reconnected with Gintoki, confiding his dream to travel through space and establish peace between humans and Amanto via mutual understanding. Gintoki supported this dream but declined to join. Post-war, Sakamoto was deceived during fundraising and thrown into the ocean. Rescued by the Chidori's Division 2 pirates, he became a slave under Vice-Captain Mutsu. During captivity, he attempted business ventures with fellow slaves, gradually gaining Mutsu's interest. Learning of a plot to execute Mutsu and the slaves, he freed the captives and orchestrated a takeover of the pirate fleet to save her. The liberated group formed the trading company Kaientai, with Sakamoto as leader and Mutsu as his second-in-command. Sakamoto is characterized by loud, persistent laughter and overt optimism, often perceived as empty-headed. He habitually dismisses danger or negative situations, leading to comedic or troublesome outcomes. Despite this facade, he demonstrates shrewd negotiation, inspirational leadership, and strategic acumen. He avoids violence when possible, preferring diplomacy and trade to resolve conflicts, reflecting his pacifist ideals. His business practices, occasionally described as sketchy, aim for mutual profit and peace between species. He exhibits fierce loyalty, defending Katsura during the war and raging when Mutsu was threatened. Notable traits include severe motion sickness (ironic given his love for spaceships), a penchant for drinking at establishments like Snack Smile, and a persistent but unsuccessful pursuit of hostess Oryou. He frequently misnames Gintoki as "Kintoki," provoking irritation. Underlying his cheer is insecurity about burdening others with deeper emotions. Later with Kaientai, Sakamoto continued bridging human-Amanto relations. He inadvertently aided Katsura by gifting him Elizabeth during trade negotiations with the Renho Tribe. During a space voyage, he reunited with Gintoki and Kagura, demonstrating willingness to sacrifice himself to save others—insisting Mutsu fire cannons at a threat even if it meant his death—before Gintoki intervened. His weapon shifted from a sword to a pistol post-injury, though his combat prowess remained significant. Leadership, economic strategy, and an unexpected talent for reading were noted as his core strengths.