Sho Yosei, alias Shou Taishi, is a central yet enigmatic figure whose true identity is Shi Shou, the most powerful of the Eight Colored Immortals and holder of the Purple Immortal title. As one of three Grand Advisors to the Emperor of Saiunkoku, he served under Emperor Senka and later his son Ryuuki, pledging allegiance not to the nation but to rulers he personally deemed worthy.

In mortal guise, he adopts the visage of a wizened elder with a flowing beard, masking his cunning intellect behind a playful, mischievous façade. His true immortal form reveals stark contrasts: long ebony hair, piercing violet eyes, and archaic robes that mirror his aloof, merciless nature. This duality enables him to manipulate events unseen while maintaining an aura of mystery.

Guided by pragmatism, Shou Taishi abstained from endorsing any prince during the imperial succession conflict, intervening only to safeguard the realm’s stability. He compelled Ryuuki’s ascension, withholding full approval until later, and engineered Kou Shuurei’s brief consortship to provoke Ryuuki’s resolve and unravel political schemes.

His relationships intertwine complexity and contradiction. He revered Emperor Senka for echoing Sou Gen, Saiunkoku’s founder, and devoted himself to Senka’s service. With Ryuuki, his interactions evolved from sardonic taunts to reluctant admiration as the emperor matured. Though subtly protective of Shuurei—showing concern for her well-being and savoring her meals—he clashed fiercely with her hot-tempered father, Kou Shouka.

Later, Shou Taishi turns his attention to Ryuuki’s daughter, Shi Chouka. Watching over her since childhood, often disguised as a crow, he shields her during her travels. Chouka’s unwavering devotion gradually erodes his detachment, prompting him to rejoin the court as Jougen after she vows to become empress—a rare concession signaling tacit recognition of her potential.

Spanning centuries, his influence shaped Saiunkoku’s foundations under Sou Gen and steered pivotal events, from commanding the Black Wolf assassins to exposing concealed bloodlines like Hyou Riou Jr.’s. Though immortal, fleeting vulnerability surfaces in moments, such as softening at Chouka’s affection, which he dismisses as anomalies. After departing following Shuurei’s funeral, he returns to guide Chouka, embodying a cyclical dance between immortal indifference and selective entanglement in mortal destinies.