Hisui is the youngest child and only son of Miroku and Sango, making him the younger brother of twin sisters Kin u and Gyokuto. He follows in his mother s footsteps by becoming a demon slayer, known as a yokai taijiya, and operates under the leadership of his maternal uncle, Kohaku, who has reestablished the demon slayer corps. His name means jade in Japanese. Physically, Hisui is a young man of average height, approximately eighteen years old, with dark hair usually tied back in a ponytail and indigo eyes. His standard attire consists of the traditional armor of a demon slayer, including a dark blue jumpsuit with green armored plates made from demon bones, along with black arm and shin guards.

In terms of personality, Hisui is serious, determined, and supportive. He is not afraid to engage in battle against demons and is always eager to help his comrades. His demeanor is generally professional and focused on the mission, and he has shown no signs of inheriting the lecherous habits that were a running trait among the men in his father s family. He is also notably naive in some social situations, though he possesses a strong sense of duty. Hisui holds a deep respect for his uncle Kohaku, whom he views as the ideal demon slayer and credits for helping him find his path in life. He was initially resentful toward his father, Miroku, believing that his father s choice to undergo one thousand days of training was an excuse to abandon the family. However, after understanding his father s true situation and seeing him in action, Hisui manages to rebuild their relationship on better terms.

His primary motivation is to protect people from demonic threats and to live up to the legacy of his family, specifically by honoring the example set by Kohaku. He appears to derive a sense of purpose from his work as a demon slayer, viewing it as a way to repay his uncle for his guidance. Within the narrative of The Second Act, Hisui serves as a supporting character and a consistent ally to the three main half-demon princesses. He often works alongside Setsuna, his fellow demon slayer, as her trusted partner. The two have a strong professional rapport and a close friendship built on years of trust. As the story progresses, it becomes evident that Hisui has developed romantic feelings for Setsuna, though he has difficulty confessing this affection, a trait he shares with both of his parents. His relationship with his older sisters, Kin u and Gyokuto, is typical of siblings; they tease him relentlessly, but they do cooperate during critical moments, such as when they helped restrain Setsuna s失控 demon blood.

Hisui s notable abilities are all centered on his combat training. As an expert combatant, he possesses above-average human strength, which is necessary to wield his primary weapon, the Hiraikotsu. This giant boomerang, made from the bones of various demons, was inherited from his mother Sango and was previously used by several generations of her family. The weapon is powerful enough to cut through a demon s natural defenses and can also absorb and disperse miasma. In addition to the Hiraikotsu, he carries a wakizashi, a short sword made from demon bone, as a secondary weapon. He is also equipped with standard demon slayer tools, including a gas mask to protect himself from miasma and deadly poison for use against enemies. Furthermore, Hisui is surprisingly well-educated. His father Miroku insisted that he not neglect learning and culture, resulting in Hisui possessing reading and writing skills far beyond the average person of the Sengoku period. He even demonstrates a talent for acting, convincingly disguising himself as his eldest sister Kin u by altering his vocal range and demeanor.