Heisuke Tōdō captains the Shinsengumi's 8th Division. Hailing from Edo, he stands as the youngest captain, known for his high energy and enthusiasm. His background identifies him as a bastard son of the Tōdō domain; he received financial support from his father under the strict condition he never seek him out. After rumors spread that he bought his rank, damaging his reputation, he left Edo and eventually joined the Shinsengumi through the Shieikan dojo, where his swordsmanship earned recognition.

Physically, Heisuke measures 163 cm, making him the shortest captain. He possesses long brown hair tied in a ponytail and cyan eyes. Following the Shinsengumi's adoption of Western attire, he cuts his hair short. After transforming into a Rasetsu—a being enhanced by the "Water of Life" (Ochimizu) elixir—his hair turns white, his eyes shift to crimson red, and his canine teeth become more pronounced [citation:].

His personality blends cheerfulness, talkativeness, and impulsive actions. He frequently forms a trio with Sanosuke Harada and Shinpachi Nagakura, often breaking curfews and drinking rules. Despite his energetic exterior, he harbors deep insecurities and struggles with depression or self-loathing, particularly following regrettable decisions. He values causes over politics, prioritizing peace in Kyoto above allegiance to either the shogunate or emperor. This conviction leads him to leave the Shinsengumi alongside his mentor, Itō Kashitarō, to join the Guardians of the Imperial Tomb, though he later questions this choice.

Key events in his story include the Ikedaya Inn incident, where he suffers a near-fatal head wound fighting Kyūjū Amagiri. During recruitment in Edo, he stays at Chizuru Yukimura's home while searching for her father. As the Shinsengumi aligns more closely with the shogunate, Heisuke grows disillusioned and departs with Itō. During the Aburanokōji incident (Itō's assassination), Amagiri critically injures Heisuke. To survive, he consumes the Ochimizu, becoming a Rasetsu. He fiercely resists his bloodlust by refusing to drink blood, relying instead on medicine to suppress it and cling to his humanity.

Later, he supports Chizuru in tracking a wounded Okita and aids Hijikata by offering his bloodlust-suppressing medicine. He participates in the Shinsengumi's relocation and adopts Western attire and hairstyle. During the Koufu Castle siege, he remains stationed in Edo with the Rasetsu unit under Sannan's command.

In the spin-off *Hakuōki: SSL*, an alternate universe portrays Heisuke as a second-year high school student and childhood friend of Chizuru. He encourages her to enroll at Hakuo Academy, and their daily walks to school deepen their bond. He realizes his romantic feelings for her, leading to a confession where he rejects her customary "friend chocolates." They eventually begin a relationship, showcasing mutual support during school events like the cultural festival, where they assist each other during busy class activities. This version emphasizes a lighter, conflict-free life contrasting his main story struggles.

His relationships feature a close mentorship with Itō Kashitarō, whose influence prompts Heisuke's temporary departure from the Shinsengumi. His dynamic with Harada and Nagakura involves frequent camaraderie and bickering, often over food. His bond with Chizuru evolves from initial protectiveness to deep loyalty; in some timelines, this develops into romance, marked by mutual understanding and shared resilience against adversity.