KAORU Tomiishi sobbed as the body of her six-year-old son Koki was lowered into a small plot near the family home in Fukuoka. She told mourners she wanted to find and kill the murderer.

Three days earlier, on September 18, the 35-year-old housewife from Japan's southern island had led a frantic search for the boy after telling police he had wandered off in a local park. Searchers found his body stuffed into a small gap in the wall of the park toilet. He had been strangled, most likely with the strap of a mobile phone.

In a depressingly familiar turn of events, investigators announced soon after the funeral that Kaoru had confessed to the "impulse" killing.

"I felt there was no hope for the future," said the mother of one, who had reportedly become overwhelmed by her parental responsibility. "I thought about killing my son and also myself."

Experts say the case is emblematic of a broader crisis. Recent statistics record more than 100 cases of maternal filicide  mothers murdering their children  since the end of 2005, including six in September this year. Although the proportion of Japanese aged 14 and younger has been steadily shrinking in the past decade, the number of filicides has stayed roughly constant.