A twenty-year-old art student. He is a former student of Shichisei Gakuen (often translated as Academy of Seven Voices), a school for fighters where Ritsu Minami was his teacher.

As ordered, Soubi contacted Ritsuka after Seimei's death. He introduced Ritsuka to the world of fighters and sacrifices, and told Ritsuka he would be his fighter. Although Soubi's "true name" is Beloved and Ritsuka's is Loveless, they fight as a pair, which is considered taboo. There is also a severe loss of strength, and in Soubi's case, his marking bleeds in battle. Since meeting Ritsuka, Soubi doesn't operate under the Beloved name, and effectively abandoned it altogether.

Soubi appears to know much more about Seimei and his cause of death than he will divulge. Despite Ritsuka's insistence that he tell him everything he knows, Soubi refuses. In volume 4 of the manga, he even says, "Seimei is my God." He openly declares that he lives his life by Seimei's orders, but still says he obeys Ritsuka's every order.

Many readers and characters in the story itself label Soubi as a masochist. He is extremely contradictory, and says conflicting things on pain and control, making his true feelings unclear. A popular theory among readers is that Soubi is selective, and only desires punishment from those he deems worthy and strong such as Seimei and Ritsuka. In support of this theory, Soubi shuns Ritsu's offers to control his life.

In addition to the masochist label, Soubi is often described as having a shotacon complex. Despite the clamor to label him as such, it is also claimed by some there is no evidence of this within the canon. Though, at least in the anime, it must be noted that Soubi is recurrently fondling and kissing the 12-year-old Ritsuka. It is difficult to explain the sexual connotations of their behavior without resorting to a shotacon-relationship; at the very least one can say their relationship is sexually ambiguous. Whether this is part of a broader complex, is unknown, though in the anime, Soubi also showed a certain infatuation with the male Zero's.