Koubun Ka (夏黄文, Ka Koubun) is the Assistant of Kougyoku Ren. He has grown up with her since she was young.
Ka Koubun is a tall man with black wavy hair tied back and yellow eyes. He has markings on his face. He wears a tall hat, with traditional and wealthy looking clothes. He carries around his Household Vessel, which takes the appearance of a green fan.
He is a cold and calm person, but seems to be more cheerful when he isn't working as Kougyoku's assistant. However, he has admitted to trying to manipulate her and his subordinates into doing what he wants, though it seems that he is not very good at this.
Koubun was born in a poor village in the North Province of the Kou Empire. He passed the National Exam with high results and was assigned as a Government Official. When he was 17, he became Kougyoku Ren's assistant and from that moment on he was always together with her.
Koubun is first seen appearing alongside his princess Kougyoku Ren saving Judar from Ugo. He begins to heal Judar as Kougyoku defeats Ugo. Once Kougyoku is asked to stop by Sinbad he retreats along with her. He is next seen alongside Kougyoku in Balbadd's palace commenting on Alibaba Saluja's decisions, saying how his argument was useless. He is greatly surprised by Kougyoku's decision regarding Balbadd's affairs. Once she leaves after this discussion, he follows.
Koubun arrives in Sindria together with Kougyoku Ren and Hakuryuu Ren. Sinbad greets them respectfully but is suddenly attacked by Kougyoku, who accuses him of deflowering her. Koubun suggested that Sinbad to marry Kougyoku for what he did. Yamraiha was able to dispel doubts of Sinbad actions by using her magic Sharrar Rakesa to re-create the true events of the night in question. It turns out that Koubun had orchestrated the entire misunderstanding, hoping to betroth Kougyoku to Sinbad and gain power over their future child. The Sindria's soldiers start to attacking him when Hakuryuu, exasperated with his countrymen's behavior, formally apologizes to Sinbad on their behalf.
Koubun's Djinn Household Vessel is a fan.
- Koubun Ka has a unnamed Household Vessel that uses the water of Vinea, to heal.
Koubun cares for Kougyoku and he's always protecting her. He's also her mentor in fencing but tends to go easy on her much to her annoyance.
- His name means Yellow Sentence in Japanese, or Yellow Culture in Chinese. His last name means Summer.
- Koubun would like to be promoted and his weakness is Kougyoku's willfulness. His special skill is to understand the human nature (self-proclaimed).