Yuushun "Yu Jun" Tei
About
His family is actually the clan of Hourins, the Ki clan, a retainer of the Kou Clan which lived secretly. Every few generations a member was chosen as the Hourin who will protect the Kou clan from its greatest danger. Before Yushuun was the current 'Hourin', the previous one was his great grandmother.
During Ensei's term as governor of Sa province, Yuushun serves as his assistant. When Ensei resigns the position and leaves, Yuushun remains there as the temporary governor, performing his duties while voluntarily locked into a tower to protect him from the Sa clan. Yuushun loses his official status and is left in a dangerous position when Shuurei and Eigetsu are appointed as co-governors of Sa province, but Ensei assures them that Yuushun will be entirely safe, even from Sakujun Sa. Yuushun first appears as an official sent from Koren to help Shuurei and Eigetsu, who had just arrived in Kinka. Under the alias of Official Yū Jun, he readily gives advice to the young co-governors. Only Ensei knows his identity, and the two men work closely together to support Shuurei and Eigetsu. Yuushun orders the military forces throughout the province to quell the riots instigated by Chuusho Sa, and to capture the corrupt members of the Sa clan. When Shuurei and Eigetsu find out that "his" tower has burned down, he reveals his real identity as Yuushun Tei and says that he was rescued by Ensei's master, who extracted him from the locked tower and left him on the streets of Kinka, where he revived the next day.
(Source: Saiunkoku Monogatari Wiki)