Sakujun Sa stands as a pivotal member of the Sa clan, biologically the son of Sa Chuushou—who presented himself as Sakujun's grandfather—making him an uncle to figures such as Sa Soujun and Sa Kokujun, not their brother. Born to a courtesan mother, he shared a half-brother in Ryou Anju. This intricate heritage entangled him deeply in Sa family power dynamics. He possesses striking physical beauty, characterized by long, wavy auburn hair and distinctive golden, cat-like eyes, favoring elegant attire chosen to complement his appearance. Profound boredom and hedonistic amorality define his personality. Outwardly charismatic and seductive, he is ruthlessly manipulative, viewing others as expendable playthings. This stems from a conviction that life lacks inherent meaning, driving him to orchestrate violence and political intrigue solely for amusement. Kou Shuurei forms his sole exception, becoming an object of obsessive focus; however, his "love" remains possessive and self-serving. His actions instigate significant turmoil within the Sa clan. At fifteen, he revived the "Murderous Blades" assassins, later employing them to murder Shunki Sa's parents fourteen years before the main narrative. He poisoned his half-brother Sa Bou and manipulated Sa Chuushou using mind-altering incense, resulting in Bou's death and Chuushou's imprisonment. His most elaborate scheme involved adopting the alias "Lin Senya" to infiltrate Shuurei's life. Tasked by Chuushou with marrying her for political advantage, Sakujun instead became fascinated by her defiance. He orchestrated Sa Soujun's death to assume clan leadership, solidifying his power to claim Shuurei. His fixation centered on her refusal to serve him "ganlu tea," a gesture reserved for those she cherished. In a final gambit, he poisoned water and placed the antidote within the tea, wagering his life that Shuurei would serve it to him. She did not, leading to his apparent death by poisoning. His last words were her name, expressing regret over never hearing her play the ehru again. His body vanished, leaving his fate ambiguous. Later, Sakujun's spirit manifested before To Eigetsu, freeing him from confinement for reasons unknown. His physical form was subsequently reanimated by the Black Immortal using Shuurei's life force, transforming him into a soulless puppet under Ryou Anju's control. Anju utilized him to attack sacred artifacts, assassinate Hyou Ruka, and kidnap Shuurei. Sakujun's will briefly reasserted itself, allowing him to aid Shuurei's escape before his body was reclaimed. His combat prowess was formidable, honed as leader of the Murderous Blades. He matched Shi Seiran in swordsmanship, demonstrated exceptional agility in evasion, and employed stealth to move undetected. His body also developed an immunity to most poisons through repeated exposure. Relationships heavily influenced his motivations. He harbored deep resentment toward Sa Enjun, whose mistreatment drove him to kill Enjun's son and daughter-in-law (Shunki's parents). His connection to Shuurei represented his only deviation from narcissism; he claimed she was the only person who "mattered," though this manifested as a desire for absolute control. He remained indifferent to other familial ties, viewing even Sa Chuushou as a mere instrument.