Ritsuko Nakajima is the mother of Youko Nakajima. Ritsuko is a well-meaning mother who, despite her stern manner, cares greatly about her daughter. Despite her own personal preferences, such as which schools she wants Youko to attend, she usually goes along with her husband's decisions as a dutiful wife. Because she doesn't want Youko to stand out or be mistaken as a delinquent, Youko's mother worries about Youko's naturally reddish hair and often tells her to cut it or dye it black. When Youko is suddenly spirited away to the Twelve Kingdoms, her fate is unknown to the people back where she was born. Youko learns about how her parents have reacted to her disappearance through the visions brought on by the Suiguutou. Youko's mother expresses worry and fear for her daughter, hoping that Youko will return and refusing to accept the conclusions that either Youko ran away out of rebellion or that she was caught up in some incident and is likely dead. As a result, Ritsuko's relationship with her husband is openly strained and she resents how her husband does not seem to care that Youko has disappeared. However, her mother becomes increasingly resigned to the idea that Youko was not as she seemed as time goes on and more people suggest that children are often not as they appear. In the anime, Ritsuko eventually learns of Youko's fate from Yuka Sugimoto when she returns from the Twelve Kingdoms; though saddened that Youko will not come back, she is satisfied to know that Youko is doing well where she is. In the novels, it is unknown if her mother ever learns what became of Youko. (Source: wikia)
Shoryu is the king of En. Like Youko, Shoryu is a taika from feudal Japan, approximately 500 years ago. He was originally the leader of a clan, and after it was wiped out, he was taken by Enki to rule the kingdom of En. Though En was originally in terrible condition, his 500-year rule has led to an extremely calm and prosperous nation. Shoryu helped Youko by providing her with an army to retake the kingdom of Kei and rescue Keiki. As a fellow taika, Shoryu feels that he should help guide Youko in her new life.
Shushou, the queen of Kyou, has ruled for over 90 years, but she has the appearance of a young girl, since that was when she was chosen to become the new ruler. She ascended the throne twenty-seven years after the death of the previous king. Though strict and capricious, she has demonstrated herself to be a wise monarch. She also appears to have above-average strength in the anime, being able to make Shoukei bow her head to her with only two fingers. The novel Tonan no Tsubasa relates her journey in the Yellow Sea and how she became the queen of Kyou.
Sekki, the brother of Koshou, is the brains behind the Shisui rebels. When Youko appears searching for Enho, Koshou is about to attack her because he believes she is a spy who is going to give them away, but Sekki stops him. He later explains that he heard the ring of steel, and that Youko's bravery suggests that she is far more dangerous than she appears. Sekki makes all the tactical decisions for the rebels except when fire threatened Takuhou and Koshou overrides him.
Koshou is the charismatic leader of the Shisui rebels. He rallies the rebels to fight against Shoukou, even though he believes that they cannot win. When Youko declares that Shoukou must be spared, Koshou supports her. When the town of Takuhou, the capital of Shisui, is set on fire, Koshou insists that the people must be rescued or else the rebellion has no point, even though the fire is a trap for his fighters. When Youko asks him what he wants as a reward for his service, he asks her to procure a university spot for his brother Sekki.
Gaishi is a friend of Kantai. After the rebellion in Kei, Gaishi becomes part of the five-man squad in charge of defending the Forbidden Gate. Before Youko Nakajima was enthroned, he was in the Baku Provincial Guard. When Risai comes to Kei and barges through the Forbidden Gate in order to beseech the ruler of Kei for help finding the missing Taiki, Gaishi appears at the gate to stop the guards from killing Risai, whom the guards believe is a dangerous intruder. (Source: wikia)
Ikuya Asano is another one of Youko's classmates who is transported to the kingdom of Kou. In the novels, Asano does not exist and Youko attends an all girls school. He goes missing after a battle between Yuka and Youko and is not seen by either of them for some time. Asano eventually becomes part of a group of Shusei and works for them as they traveled through the kingdoms. However, being in a completely alien country and lacking the ability to speak or understand the language, the strain has taken a toll on his sanity. Eventually, Asano questions the reason he was ever brought to Kou and seemingly can't find a reason for his life to go on. He dies at some point later in the anime.