a twenty-five episode anime television series broadcast on TV Tokyo from October 1, 2002 until March 25, 2003. The anime is licensed in Region 1 by Funimation, who released it on DVD and broadcast it on the Funimation Channel, along with the programming block on Colours TV in 2006. The series was also adapted as four light novels and a series of CD dramas.About two years ago, Ayumu Narumi's older brother Kiyotaka, a famous detective and pianist, mysteriously disappears without a trace. Ayumu's only clue as to his brother's whereabouts is the phrase "Blade Children," the only words Ayumu could make out in Kiyotaka's final phone call. Now in his freshman year of high school, Ayumu becomes involved in solving in a series of murders, crimes, and other incidents, all related to the Blade Children. Together with his school's journalist, Hiyono Yuizaki, and the unwilling assistance of his sister-in-law, Madoka, Ayumu tries to figure out who the Blade Children are and what are their goals.

The Blade Children are the central mystery of the series, known only as cursed children that few know about and are being pursued by so-called Hunters. They are distinguished by their cat-like eyes (though a few lack this feature) and by missing the seventh right rib bone. As Ayumu investigates them, he meets five Blade Children Kousuke Asazuki, Rio Takeuchi, Eyes Rutherford, Ryoko Takamachi, and Kanone Hilbert, and is tested in various ways by them. Those who meet him eventually conclude, some more reluctantly than others, that Ayumu does have what it takes to "save" the Blade Children, as they say Kiyotaka claims.

The anime series, which adapts the story through the sixth volume of the manga, compares the Blade Children to cuckoo birds, having been deposited in human "nests" to be raised, and suggesting that cuckoos go violently crazy toward the end of their lives. The manga continues the story, depicting Ayumu's discoveries about the origin of the Blade Children, their relationship w