Now his parents are seeking to turn their heartache into a windfall. In their provocative new book, “Giving Birth to ‘Boy A’,” they attempt to explain how an ordinary salaryman and his wife came to raise the most notorious teenage killer in Japanese history. (The title was chosen to protect the offender’s family, in accordance with Japanese law; the authors are listed only as “The Parents of Boy A.”) Launched in April by the prestigious publisher Bungeishunju, the book has sold nearly half a million copies and has dominated best-seller lists all over the country. It has also triggered a Japanese version of the “do we really know our kids?” hysteria that has swept America since 15 people died in April at Colorado’s Columbine High School. The authors have received about 400 letters, mostly from women readers “in their late 30s or early 40s,” says publisher Takashi Fujisawa, who “wanted to know why the murders happened, what his family background was like and details of the parent-child relationship.”

When Boy A’s case broke two years ago, it shattered the myth of Japan as a nation of well-adjusted, nonviolent kids. His killing spree focused attention on an alarming upsurge in youth crime. Most disturbing for a country with the lowest crime rate of any industrialized nation: a huge spike in violent juvenile crime, including rape, assault and murder. The bulk of those crimes were committed by “normal” kids from “average” families with no prior behavioral problems. Experts blame Japan’s rigorous test-based education system for a growing sense of alienation among many young Japanese. The rise of two-income households where both parents work has left more children unsupervised and isolated. “Japanese children have changed so drastically during the last decade,” says Ryoichi Kawakami, a veteran junior-high-school teacher. “They cannot relate well to other people. We really don’t know them anymore.”

In “Giving Birth,” Boy A’s parents combine accounts of their eldest son’s childhood with descriptions of the period following his arrest. Perhaps the most remarkable thing about the family is how utterly unremarkable it is: Dad works too hard as a salaryman, Mom is loving but overbearing. Boy A is a quiet, sensitive boy who once begged his mother not to crush cockroaches in the kitchen. But apparently he acted quite differently at school, remarking that human lives were no different from those of cockroaches and creating bizarre monsters out of clay. “I didn’t know my own son until the incident,” Boy A’s mother writes. “I am so ashamed of myself, but I honestly didn’t know.”

Many critics find that hard to believe. Some reviews of the book have portrayed its authors as tuned-out parents who missed blatant warning signs. At one point Mom laments the lack of obvious antisocial behavior in her son “like dying hair, body piercing or joining a motorcycle gang.” But she admits she failed to register his penchant for shoplifting thermometers, from which he extracted mercury to poison cats. Until police raided their home, the book claims, Dad didn’t realize that Boy A’s room had a passage to the attic, where he hid the second victim’s severed head. Police also found a sake jar full of cat tongues in his room. “My impression [of the mother] was that she tried to look away,” says Yoko Kurahashi, a 46-year-old writer and mother. “She saw him the way she wanted him to be.”

The book is full of apologies. Boy A’s parents say they decided to publish their account in response to the widespread demand for more knowledge of their son and his childhood. They plan to use all royalties to pay off damages to the families of their son’s victims. But for the father of Jun Hase, the 11-year-old Boy A beheaded, no amount of money will ever be enough. “[My son] Jun’s soul won’t be saved with this book,” he wrote in the Weekly Shincho in May. “It contains nothing but excuses and evasions full of ‘We didn’t know’ and ‘We didn’t notice’.” But thanks largely to the book, most Japanese parents have their eyes open now.