Hijikata Toushirou is the former Vice-Commander of the Shinsengumi, a special police force in Edo. Widely known by his fearsome epithet, the Demonic Vice-Commander, he is the strict and dedicated brain behind the organization, having formulated the rigid disciplinary framework that governs its members. His reputation for ruthlessness strikes fear into both enemies and his own subordinates, with only a few close companions exempt from his intimidating demeanor.

Hijikata's background is marked by hardship. He was born as the illegitimate son of a rich farmer and a mistress, and his father died before he was born. After losing his mother, he was taken in by his older half-brother, Tamegoro, who became a father figure to him. When Hijikata was eleven, a fire broke out in their village and bandits used the chaos to attack. Tamegoro shielded him from the assault, losing his eyesight in the process. Consumed by an uncontrollable rage, Hijikata retaliated against the bandits with a knife, injuring their eyes in a manner similar to the wounds inflicted on his brother. His other siblings witnessed this act, and the fear in their eyes led him to become known as Thorny Toshi. Unable to remain with his beloved brother, he left home to become stronger, leading the life of a wandering and troublesome ronin.

His path changed when he was taken in by Kondou Isao, the man who would become the Commander of the Shinsengumi. At Kondou's dojo, he met the Okita siblings. He formed a deep, unbreakable bond of loyalty with Kondou, whom he views as the very soul of the Shinsengumi. Conversely, his relationship with Okita Sougo has always been fraught with tension, partly because of Sougo's jealousy over the attention Hijikata received from both Kondou and his sister, Mitsuba. Before leaving for Edo, Mitsuba confessed her love to Hijikata. He rejected her, believing that his violent life could never bring her happiness, a secret he carries with him always.

In his role as Vice-Commander, Hijikata is the primary enforcer of order and strategy. He is a short-tempered individual who is often seen reprimanding others and threatening them with severe punishment. Despite his cold and strict exterior, he has a hidden compassionate side and is willing to help those in need, though he typically veils such kindness with exaggerated annoyance. He is fiercely proud and stubborn, disliking any display of weakness.

Hijikata is notorious for his two overwhelming obsessions. He is a chain-smoker, rarely seen without a cigarette. His other great love is mayonnaise, which he pours onto virtually any food, including desserts, creating dishes known as Hijikata Specials. His personality is remarkably similar to that of Sakata Gintoki, a fact that has been noted by other characters. This similarity leads them to frequently clash as rivals but also to reach an incredible level of synchronization when fighting together, sharing similar fears such as a terror of ghosts and dentists.

In terms of abilities, Hijikata is a highly talented and powerful swordsman, capable of taking on numerous enemies single-handedly. His strategic mind makes him the tactical core of the Shinsengumi. At one point, his worn-out sword was replaced with a cursed blade named Muramasha. This sword contained a vengeful spirit that manifested a split personality within him: Tosshi, a weak-willed and cowardly otaku obsessed with anime and figurines. Hijikata eventually managed to overcome this influence with the help of others.

Throughout the story, Hijikata remains a central figure. He navigates numerous arcs that test his loyalty and strength, from internal plots to overthrow the Shinsengumi to large-scale battles against powerful enemies. He demonstrates unwavering dedication to protecting Kondou and the Shinsengumi's honor, even when the organization is officially disbanded. His development sees him confronting his past, reconciling his feelings for Mitsuba after her death, and continually fighting alongside his unexpected ally, Gintoki, to protect the future of Edo.