Although Karen is his Ten no Ryuu companion, he has interaction with the rest of the Dragons as well.

Shirou Kamui is the one destined to decide the fate of Earth. Following the death of his mother, he returned to Tokyo, only to find himself and everyone he loved involved in the end of the world. He can either protect life as it is, or destroy the human race so the Earth can heal. At first he rebels against his fate, but his love for his two childhood friends (Fuuma and his sister Kotori) causes him to decide to protect life on Earth. The tragedy is that Fuuma turns out to be his twin star—the person who will take the opposite side of whatever Kamui chooses. He kills his own sister and casts away his former identity as Fuuma and takes on the title of “Kamui”. Kamui is brokenhearted, but decides he will still protect the world where his friend lives.

Kamui is reluctant to make friends, but Seiichirou doesn’t appear to be put off by his attitude. He seems to sympathize with the young man’s situation and is supportive without being domineering. His kindness eventually wins Kamui over and he comes to see Seiichirou as a father figure.

Arisugawa Sorata is an upbeat young man who has embraced his destiny. When he was a young boy, the Stargazer Chuu determined that Sorata would be one of the Ten no Ryuu and took him from his parents so that he could be trained in the monastery. Years later, Sorata forgot the faces of his parents, but he remembered that his mother was crying as he was taken away. As a result, he hated to see women cry. He was pleased when the Stargazer made another prediction—he would fight to protect Kamui, but he would die for the woman he loved. He decided that she would be someone beautiful. Upon meeting a fellow Ten no Ryuu named Arashi, he declared that she was the one for whom he would give his life.

Sorata isn’t terribly close to Seiichirou, but they have a lot in common. Even though their destinies are rather dark, they remain light. While both can be serious when needed, they also have a sense of humor. Both appreciate the “normal” things in life. They like each other and get along well.

Kishuu Arashi is the Hidden Priestess Ise Shrine and the barer of a sacred sword which she summons out of her hand. Her mother left the shrine to give birth to her, but died leaving her daughter on the street. By the time Arashi’s grandmother found her, the young girl was half starved and indifferent to her own life Eventually her grandmother convinced her to eat and live, but Arashi was still distant and cold, until she met Sorata. At first she kept him at arm’s length and seemed to be annoyed by his attention. As time went by it became clear that she was falling in love, and when Sorata got seriously injured she finally confessed her feelings.

Seiichirou met Arashi while she was in a battle with a bunch of shiki. He walked right into her kekkai (which only those involved in the end of the world can enter) and helped her defeat the shiki with his wind powers. He gave her his business card and an umbrella to protect her from the rain. The two are friendly, but not very close.

Nekoi Yuzariha, the youngest member of the Ten no Ryuu, hails from the Mitsumine tribe. Cheerful and friendly, Yuzariha seems like a fairly typical teenager. Her companion is a dog spirit named Inuki which can transform into a sword. As a child, she was sad to learn that other children could not see Inuki, and she decided that she could only love someone who could see her friend. Before meeting the other Ten no Ryuu, she met an older man who patted Inuki on the head and she was so happy that she embraced him. Unfortunately the man, Shiyuu Kusanagi, was one of the Chi no Ryuu. Still, she can’t help loving him and he seems to care about her as well.

While she is closer with the younger Dragons, she likes Seiichirou and met him at some point before joining the Ten no Ryuu.

Sumeragi Subaru is the thirteenth head of the Sumeragi Clan and a very powerful onmyougi. The tragic story of his past is told in Tokyo Babylon. He fell in love with a man named Sakurazuka Seshirou, a kind hearted, but very flirtatious, vet. Even Subaru’s beloved sister Hokuto encouraged the relationship. In reality, Seshirou was dark onmyouji who had made a bet with Subaru when they were young. Sometime in the future, he would spend a year with Subaru and if he could feel anything for him at all, he would stay by his side forever, but if not, he would kill him. Before locking away the memory in Subaru’s mind, he marked him as prey of the Sakurazukamori. After the year was over, he declared that he felt nothing for Subaru and planned to kill him. Subaru went into a state of shock and could not be revived. To save him, Hokuto took his place and died. Having lost his sister to the man he loves, he joins the Ten no Ryuu with one dream left, but will it ever come true?

Subaru is far too busy being Emo to have much of a relationship with Seiichirou. Still, they have met and interacted a bit.