Junkou (馴行) was the younger brother of Shishou, the king who preceded Kouko. He was appointed the rank of Taiho, a member of the Sankou who serves to advise the king. Described as the polar opposite of Shishou, Junkou was known to be a trusting and straight-forward man of discretion, and had loyally followed his brother's faction against Fu-ou. Well-aware that he was not as talented as Shishou or his cousin Eishuku, Junkou nevertheless followed Shishou without any negative feelings towards him.
During the events of the short story Kasho, Junkou mysteriously goes missing after the death of Daishou, the Taishi and the father of both Shishou and Junkou. Before his disappearance, Junkou had been attempting to deliver Sai's royal treasure, the kasho kada, to the king. His disapperance lends to Shishou's conjecture that members of the court, including his cousin Eishuku and Shuka, Eishuku's wife, are conspiring against him to cause his reign to fail.
In order to prove their innocence, Shuka convinces Seiki, Eishuku's undersecretary and foster-brother, to reveal a conversation that Seiki had with Junkou prior to Junkou's disapperance. Seiki admits that during the conversation, Junkou had confessed to feeling that if Shishou succeeded in creating his ideal kingdom of prosperity, he would not have a place in it. As a person of ordinary capabilities, Junkou seems to have had a grounded sense that his brother's idealism could not apply to reality.
Junkou's body is later found in a remote palace with the abandoned and partially broken kasho kada. Upon noticing the unusual nature of Junkou's death and the resigned nature of Junkou's words, Seiki suggests that Junkou may have used the kasho kada to see what he believed to be an ideal world. This suggestion causes Shuka to realize who is responsible for causing the deaths of Junkou and the Taishi, as well as who was responsible for inciting the culprit to such actions.