Ayumu's older brother, who is perfect at everything in the eyes of Ayumu. He became a world-class pianist after the age of ten and then an unimaginable world-class detective at twenty. He married Madoka - but left a year after they married. He is also the real reason why Ayumu always doubts himself, who is constantly comparing himself to him. Kiyotaka left one day after he was researching the mysterious case of the Blade Children. Many assume he is now dead. Ayumu discovers that he is not, after hearing that he has been associated with the Blade Children. (Source: Wikipedia)
One of the most down-to-earth person of the Blade Children; Ryouko is a clever and athletic person, probably the most athletic of the Blade Children. She is a natural-born runner and can outrace almost anyone. She is a childhood friend of Kousuke Asazuki and, unlike the other Blade Children, she despises killing. She dislikes Eyes Rutherford due to past issues and cares deeply for Kousuke, though she has a tendency to use him as a punching bag and make him buy her food. Her past is relatively unknown, though it is hinted that something traumatizing happened while Kousuke and Eyes were present. She is relutantly brought back into the conflict of the Blade Children by Eyes after losing to him in a simple game of dodge ball. She honors their deal to join with the rest of the Blade Children, with only one condition: she will not kill anyone. She is still with Kousuke and hopes to run in the Olympics. (Source: Wikipedia)
Grampa Theo is an old puppeteer who used to travel around Italy with his son, Leon and granddaughter, Nana. He and his son had arguments regarding Leon's dream to become a doctor. Grampa Theo did not want Leon to become a doctor. He wanted his son to take over his puppet shows, but Leon, who is completely uninterested to become a puppeteer, refused to do so. One day, Nana, then an infant, got very sick. Little Nana luckily recovered from her sickness later. The argument between Grampa Theo and his son got worse because of what happened to Nana before. It reached to the point that Leon left his family. Few years later, Grampa Theo and Nana, now an older little child, moved near the Rossi family's house in Milan after hearing a rumor that Leon is in the city mentioned. By the request of Angeletta, Romeo searched for Leon. In the end, Romeo, with the help of Professor Casella, found Leon, who is now a doctor of poor children in Milan. Grampa Theo and Little Nana were reunited with now Dr. Leon. The father and son reconciled with each other.
The world-class pianist, he is second only to Kiyotaka Narumi, Ayumu Narumi's older brother. He is seemingly cold-hearted but definitely not heartless (he brought Rio melons when she was stuck in the hospital). He cares a great deal about the Blade Children and would do anything for them to survive at all costs. He is exceedingly loyal to Kiyotaka's words and seems to believe in Ayumu the most out of all the Blade Children. Eyes knows much more than the other Blade Children do, holding secrets he keeps to himself. He is one of the first targets of assassination by the Hunters (after Sayoko) but outwits them at a charity concert with the help of Ayumu and Kousuke. He and Kanone have a some sort of bond, even though the friendship between Eyes and Kanone seems to shatter once he learned of Kanone's betrayal of the Blade Children. Eyes appears to be the leader of the Blade Children but he treats Kanone as either an equal or even an older brother. (Source: Wikipedia)
Lady Susan is a member of a league of American superheroes apparently led by Dr. Riddles, The Majestic Twelve. Her power includes bouncing her breasts up and down or shaking them with her arms to distract everyone. She is the most prominent of the twelve, appearing occasionally on her own and consistently seen alongside Dr. Riddles. She also, on occasion, is shown as actually able to fight. Her dialogue consists almost exclusively of the word "Yay". (Source: Wikipedia)