Sou Shungai occupies the prestigious position of Taifu (太傅), or Grand Protector, one of the three Grand Advisors to the Emperor of Saiunkoku. Holding the Senior First Court Rank, this role stands as the third-highest among the imperial advisory positions. He served both Emperor Shi Senka and his successor, Emperor Shi Ryuuki, maintaining his post until the conclusion of his tenure.

A decorated war hero and former general, Sou Shungai commanded significant military expertise. He trained the imperial army and personally instructed princes Shi Ryuuki and Shi Seien in swordsmanship during their youth, his background as a military leader cementing his formidable reputation at court.

Sou Shungai maintained steadfast loyalty to the imperial throne throughout his long service. He remained an advisor far longer than his counterparts—Sho Yosei (Taishi) and Sa Enjun (Taiho)—who both vacated their positions earlier due to political turmoil and personal sacrifices. His close association with Advisor Sho included awareness of Sho's intricate schemes and the existence of the covert Eight Immortals, placing him at the heart of high-level court intrigues.

Unlike the other Grand Advisors, Sou Shungai's tenure concluded without controversy. He continued advising Emperor Ryuuki until his eventual departure, leaving the Taifu seat vacant after a lifetime of dedicated service. His legacy encompasses mentoring key imperial family members and strengthening the military foundations of the Saiunkoku government.

Collectively, the Three Grand Advisors mirrored the ancient Chinese Zhou Dynasty's Three Ducal Ministers, embodying the emperor's most trusted mentors and administrators.