Ritsuka Aoyagi is a sixth grader, transferring to a new school. Years ago his brother Seimei was murdered. Upon transferring in, he is branded as peculiar - he shows up without his parents, and is aloof toward the other students. Yuiko, an outcast in her own right, befriends him, much to his dismay. Soubi, a Fighter Unit, arrives to meet Aoyagi. Soubi knew Seimei, and Aoyagi lets his guard down momentarily. Midori and his Fighter Unit Ai come with orders to abduct Aoyagi, but are powerless against Soubi. Aoyagi, who seems to be suffering from memory loss as well as personality disorder, wants to reclaim his identity as "Ritsuka." Aoyagi discovers a mysterious last message left from Seimei in which he reveals the identity of his murderer(s) as The Seventh Moon, and that his true name is Loveless. Midori and Ai again try to abduct Aoyagi, but are thwarted once again by Soubi. Aoyagi is confused by Soubi's psychological tactics, who seduces him yet withholds the emotional connectivity which he craves. On the other hand, he slowly warms up to Yuiko, becoming a friend to her.
Meanwhile, other rivals appear: Yayoi is jealous of Aoyagi's friendship with Yuiko; and Kio, a university colleague of Soubi, is distraught that a young boy such as Aoyagi could capture Soubi's attention. As a sign of their bond, Soubi asks that Aoyagi pierce his ears. On Parents' Day at school, neither Aoyagi nor Yuiko's parents are present, but Soubi shows up to greet Aoyagi at the entrance. Aoyagi is further entranced by Soubi.