Sanosuke Harada was born in 1840 to a low-ranking quasi-samurai family in the Iyo-Matsuyama Domain. He mastered the Hōzōin-ryū spear technique, favoring it over the sword. A defining moment came when ridicule by a higher-ranking retainer drove him to attempt seppuku; he survived, bearing a prominent stomach scar he later displayed as a badge of resilience. This scar inspired his personal crest: a horizontal line within a circle. He moved to Edo, training at Kondō Isami's Shieikan dōjō. In 1863, he joined the Rōshigumi, staying in Kyoto with Kondō to form the Mibu Rōshigumi, later known as the Shinsengumi. As Captain of the 10th Division, Harada participated in pivotal events including the Ikedaya incident, the Sanjō Seisatsu incident, and the assassination of Itō Kashitarō. He married Sugawara Masa in 1865; their son Shigeru was born in 1866, followed by a second son who died in infancy. Harada possessed a short temper and occasional insubordination, balanced by fierce loyalty and devotion as a husband. Following the Battle of Toba–Fushimi in 1868, Harada relocated to Edo with his family. After the Shinsengumi's defeat at Kōshū-Katsunuma, he and Nagakura Shinpachi departed due to disagreements with Kondō over the group's future structure. They founded the Seiheitai, but Harada returned to Edo for his family. Unable to leave the city, he joined the pro-Tokugawa Shōgitai. At the Battle of Ueno, he sustained severe gunshot wounds and died two days later on July 6, 1868. Alternate, unverified accounts claim he survived, fled to China, led horse-riding bandits, and aided the Imperial Japanese Army during the First Sino-Japanese War. Fictional portrayals depict Harada as one of the Shinsengumi's most cheerful and approachable captains, often lightening moods with jokes alongside friends Nagakura and Heisuke Tōdō. Despite his generally laid-back demeanor, his fierce temper flared when protecting secrets or principles, such as punching Heisuke for nearly revealing sensitive information. He is highly protective, particularly of women and children, frequently emphasizing a man's duty to safeguard them. This extends to his bond with Chizuru Yukimura, whom he comforts during distress and defends against supernatural threats. His narrative arc shows initial loyalty to the Shinsengumi, followed by departure with Nagakura over ideological differences regarding Kondō's ambitions. He later resurfaces to combat antagonist Koudou's forces, suffering near-fatal injuries. In one storyline, he survives, escapes Japan with Chizuru, marries her, and fathers a son named Shigeru, living quietly abroad until reuniting with allies like Shiranui. In the spin-off *Hakuōki: SSL*, set in a modern high school, he serves as Chizuru's homeroom and PE teacher. This adaptation retains his protective nature and charm while introducing a power dynamic as he navigates forbidden feelings for his student, referencing original-era traits like taking her to the beach, echoing their life overseas in other media. Across all iterations, Harada remains human, never becoming a Rasetsu. His core traits—honor, loyalty, a blend of joviality and intensity, and a yearning for family—persist regardless of timeline.