Shi Seiran serves as the sole retainer of the Hong household. Though presenting as early twenties, he is actually twenty-six at the series' start, possessing gray shoulder-length hair, black eyes, and a notably handsome appearance reminiscent of his father. He maintains an amiable disposition but exhibits ruthlessness towards threats to his loved ones, believing the end justifies the means.

Thirteen years prior, Kou Shouka and Shokun Hong discovered him injured during a family trip and adopted him. Shokun named him "Seiran" (Silent Orchid) for his initial muteness and gave him the surname "Shi" – sharing pronunciation with the imperial name but using different kanji. Seiran vowed lifelong loyalty to repay them, performing household repairs, guard work, and protecting the family. His true identity is Shi Seien, the exiled second prince of Saiunkoku, following a failed succession plot by his maternal relatives that resulted in his mother's death by assassins. Renowned as the intellectual and combative "flower" of the princes, his exile stranded him in Sa Province, where he joined the Satsujinzoku bandits under the moniker "Little Whirlwind." He later dismantled the group with fellow member Ro Ensei.

After joining the Hong family, he suppressed his past, though some eventually discover his lineage. He is intensely protective of Kou Shuurei, whom he has known since childhood, often shadowing her discreetly. Their closeness leads others to mistake them for a couple, though no romantic feelings exist between them. Having experienced poverty, he developed frugal habits and opportunistically solicits money from wealthier acquaintances like Ran Shuuei and Shin Suou.

Following Shuurei's entry into palace service, he became Emperor Ryuuki's bodyguard, leveraging his combat expertise and perceptiveness to advise against political plots. He accompanied Shuurei to Sa Province as governor, confronting his nemesis Sa Sakujun, who had forced him into the bandits. Later, he remained in the capital to protect Prime Minister Tei Yuushun while Shuurei undertook missions, reducing their interactions.

His skills include masterful swordsmanship (using the sword Bakuya gifted by Ryuuki), precision archery, and poison detection. His relationships include unwavering devotion to the Hong family; a mentorship-turned-advisory role for Ryuuki, whose admiration he reciprocates; and guarded interactions with former associates like Ensei.

In later years, he serves as a protector and unofficial advisor to Empress Shi Chouka, Ryuuki and Shuurei's daughter, while maintaining discreet oversight of imperial stability. His primary motivation remains fulfilling his vow to the Hong family through silent guardianship.