Aya is a silent man whose sister is in a mysterious coma. His parents were killed and his sister run over by Reiji Takatori, and thus he joins Weiss¸ seeking only revenge. As a constant reminder of the purpose behind his actions, he takes on his sister's name and wears one of her earrings, which actually were a gift from him to her. Because of his past tragedy and current resolve, he is strongly silent and seems very cold. Although Omi is the official leader of Weiss, Aya wields a great deal of authority over the team during their missions. His real name is Ran Fujimiya.

Due to his computer skills, Omi is in charge of gathering information and planning Weiss¸'s missions. He doesn't remember his life before Kritiker (the underground crime-fighting organization Weiss¸ is commissioned by) at the start of the series, but as the action unfolds he discovers he is in fact Mamoru Takatori, son of Reiji Takatori - head of the Takatori family, who are in some way related to almost all the missions the boys have to take. He has a tough time trying to figure out where his loyalty should lie, but in the end realizes that what he truly desires is to stop the corruption his biological family spreads. Later, in the Dramatic Precious drama CDs, he finds out that he is really Shuichi Takatori's biological son, and this is the reason he assumes the position "Persia" in Glühen.

Ken was once a talented professional soccer goalie in the J-League, he was forced to quit due to a gambling scandal, despite the fact that he was completely innocent. It turns out his best friend, Koichiro Kase, drugged him so he would throw a game in favor of the gamblers. Ken doesn't know this, however, and is beaten up and left for dead in a burning warehouse when Kase tells him he found the leader of the gambling ring who set Ken up in the first place. Ken doesn't discover Kase's lies, believing him long gone, until he meets Kase some years later, attempting to figure out why his best friend is one of Weiss¸'s targets. In the end, Kase, who is working very close under a man whom Weiss¸ needs to kill, sets Ken up once more, giving him a false lead and then shooting at Ken himself. When Kase sees him one last time, Ken doesn't grant him any mercy, although he is tormented by his actions afterwards.

Yoji is a ladies' man and a former private detective. We discover by way of some painful flashbacks and explanations on Yoji's part that he once ran a Private Investigator Agency with his first love, a young woman with sunglasses and a distinctive beauty mark named Asuka Murase. Asuka, however, was shot and killed while investigating the members only Liott club, which hides a prostitution ring. He joined Weiss¸ to protect all the other women of the world because he couldn't protect his love and partner, and this explains his insensitive-seeming practice of only accepting missions that have to do with women of legal age.