Hisui, the Earth Byakko among the Eight Guardians, protects the White Dragon Priestess in a Heian-inspired parallel world. Commanding a pirate crew from Iyo Province, he maintains neutrality in the capital's imperial conflict. Standing 183 cm tall, he has teal waist-length hair and matching eyes, typically wearing a kimono with earrings. The Dragon Star Spindle—a rope with weighted ends—wraps around his torso as his weapon. Despite his piracy, he displays refined tastes: enjoying flower viewing, favoring Jijuu's scent, the color silver, and seasonal blooms like golden lace and satsuma. His preferred locations include Shirakawa, Suzaku Gate, and Fushimi Inari. Born Masahiro Tachibana, he descends from a family that served in the national guard and governed Iyo. At age ten, he learned his ancestors rebelled against corrupt imperial governors, prompting his father to abandon piracy for capital life. When the Tachibana main house pressured him to become heir, he rejected nobility, adopted the name Hisui, and embraced his forebears' piracy. By twenty-five, he led an uprising against Iyo's oppressive governor and later collaborated with Yukitaka Fujiwara, the new governor, to peacefully disband pirate factions. This cooperation lasted six years, though Hisui viewed Yukitaka as naive in negotiations. He maintains no ties with his estranged parents or younger brother. His initial capital involvement begins with a noble's letter seeking pirate scapegoats for a plot. Intrigued by the sender's arrogance, Hisui travels alone to meet them while his crew hides. He rescues the newly summoned priestess, Karin, from human traffickers during her first night in this world. Though repeatedly offering her escape from guardian duties—citing their lack of obligation to the capital—he stays as her protector under the guise of self-amusement. He covertly updates his crew and evades authorities while accompanying her. His dynamic with Yukitaka remains contentious; he openly mocks Yukitaka's diplomacy during encounters with antagonists like Shirin. His relationship with Karin drives his evolution. Initially apathetic and self-serving, he achieves his goal of rejecting the noble Kazuhito in person but remains with Karin due to growing fascination. After witnessing her seal vengeful spirits, he embraces his guardian role earnestly. He reluctantly shares his clan's history and belief in universal solitude—rejecting loyalty or obligation—during private talks with Karin. His perspective shifts when he instinctively shields her from a possessed onmyouji's attack, sparking introspection about his changing feelings. Later, he confesses his desire for her companionship, inviting her to join his adventures. Following these events, Hisui considers abandoning piracy to stay in the capital, prompting his crew's frantic search. In later media like "Yume no Ukihashi," he assists the priestess as a starting guardian or helps break seals imprisoning other guardians, using a compact mirror to dispel illusions.