Hajime Saito, Captain of the Shinsengumi's Third Division, is renowned for his exceptional left-handed iai swordsmanship. His sharp rationality, emotional distance, and reserved nature often project a cold, stoic demeanor. Yet beneath this lies a capacity for empathy and thoughtful consideration, particularly towards Chizuru Yukimura; he once acknowledged her vulnerability as "nothing more than a lone girl looking for someone to help her" while claiming an inability to sympathize.

Saito displays unwavering loyalty and obedience, rarely questioning orders regardless of their nature. This dutifulness leads him to frequently undertake the Shinsengumi's most morally complex or violent tasks, sometimes prompting accusations of lacking personal will. However, he proves capable of defying commands when conscience demands, such as choosing to fight alongside the Aizu forces at Bonari Pass instead of heading north with the Shinsengumi. His matter-of-fact delivery and controlled demeanor make him an effective deceiver, successfully infiltrating and spying on the Guardians of the Imperial Tomb for months.

Beneath his stoicism, Saito exhibits notable shyness and discomfort around women, struggling to initiate conversations with Chizuru outside necessary communication. This social awkwardness surfaces in visibly flustered reactions when his feelings are mentioned, like looking away when charmed by her appearance during her geiko operation or denying emotional attachment when teased by Okita. He remains largely unaware of his own romantic feelings, failing to recognize jealousy when others show interest in Chizuru.

His past reveals early adversity; no dojo accepted him due to his unorthodox left-handed style until a duel with Okita Souji at Shieikan ended in a draw, demonstrating the unpredictable advantage of his technique and securing his acceptance.

Saito's narrative journey shows significant development. Initially detached and willing to follow orders to eliminate Chizuru if commanded, he gradually demonstrates protective instincts and concern for her well-being. Early actions include testing her combat abilities, offering guarded reassurance, and advising her against dangerous inquiries. Key moments, like discreetly allowing her to leave her room against Hijikata’s orders to resolve a crisis, signal his willingness to prioritize her safety over strict compliance.

In later continuations, particularly "Ginsei no Shou," his character arc resolves. Surviving the war, he lives with Chizuru as a married couple in Tonami under Aizu exile. They share peaceful moments like viewing cherry blossoms, where he reflects on samurai transience but firmly rejects a warrior’s death, vowing never to use the Rasetsu power again to avoid leaving Chizuru alone. He secures a role representing Aizu in a new government police organization, echoing the Shinsengumi’s duties. The story culminates with Chizuru revealing her pregnancy, bringing him profound happiness after previous difficulties conceiving, leading him to propose a shift to more intimate forms of address, signifying deepened emotional connection.

His combat prowess is consistently highlighted, mastering quick-draw techniques suited to his left-handed style. His signature efficiency involves taking no pleasure in combat but executing it with brutal skill. Specific techniques like the thrust-oriented "Gatotsu" draw inspiration from historical accounts of his swordsmanship, though its fictionalized portrayal varies across adaptations.