In playgrounds and in preschools across the U.S., parenting has become a competitive sport. Taking their children's success as a sign of their own, mothers often go to extremes to win them entree into the "right" programs and cliques. But could the increasingly high social stakes ever drive a mother to commit murder? Consider what's happened, more than once, in Japan . . . As Mie Taniguchi sped along a deserted country road one Friday in February of 2006, she felt tired and spent. For the past few nights, the 34-year-old had been unable to sleep as she struggled with her feelings of loneliness. As happens with many women in Japan, Taniguchi's only friends were the mothers at her daughter's kindergarten-but recently, they had been distant, and she felt bitterly excluded. Now, she was afraid they would reject her 5-year-old daughter, too.

This morning, it was Taniguchi's turn to drive her daughter and two of her classmates to their kindergarten in Nagahama. In the backseat, Wakana Taketomo and Jin Sano sat quietly, staring sleepily out the window. Taniguchi mistook their silence for a deliberate snub of her daughter. That idea pushed her over the edge.

Hitting the brakes, Taniguchi pulled off the road, reached into her handbag, and drew out a thin-bladed fish knife. As the children screamed in horror, she launched a frenzied attack, stabbing Wakana 19 times and Jin 13 times. Ignoring her daughter's terrified pleas, Taniguchi dumped Wakana on the side of the road and threw Jin into an irrigation ditch. When a passerby discovered them 30 minutes later, the children were alive but just barely-Wakana was declared dead at 9:45 a.m., and Jin died a few hours later.

Taniguchi was found, shocked and bloodied, in her parked car with her daughter some 35 miles away. In her police interview, she poured her heart out-about being ostracized by the other mothers, about being forced to feel like she and her daughter weren't good enough to belong. The media was unsympathetic; Taniguchi was portrayed as a cold-blooded killer.

In private, however, many Japanese mothers could relate. "A lot of women share that feeling," admits Hiroko Kusama, a teacher and single mother in Shiga. "Not as far as killing-but a lot of women are one step short of that."

Virtually every park and kindergarten in Japan has a "mommy clique"- a close-knit group of women who socialize while their children are on playdates and visit cafes together when they're at school. Mimicking the country's strict corporate hierarchy, cliques are governed by a "boss mom," to whom the other mothers defer, and competition within the group can be intense.

For Taniguchi, belonging was everything. If she was accepted by these well-connected middle-class mothers, her daughter could look forward to a lifelong social network, good job prospects, and marriage to a well-off man.

But it wasn't easy. From the start, the other mothers treated her with disdain. As a Chinese immigrant, she found the nuanced customs of Japanese society difficult to grasp, immediately marking her as an outsider. And although her husband had a good job with a manufacturing company, she wasn't as well-off as others in the group. However much she tried to fit in, Taniguchi was frequently excluded from their text-messaging and dates.

But the real cause of Taniguchi's breakdown was her daughter's treatment by her classmates. "I felt the children were to blame for my daughter not getting along [at kindergarten], so I killed them," she told police.

"Socializing in Japan is far more intense than in other countries," says Carol Hui, a Canadian mother of two who lives in Tokyo. "Mothers who don't work spend so much time with other mothers, they've almost replaced the family unit. Whether a woman is accepted by the other mothers determines her entire social life and how her child will be treated."

Like other aspects of Japanese society, joining a mommy clique is highly ritualized. Mothers and their children first make their "park debut": Smartly dressed, they arrive at the park at the start of the week and approach other mothers and their children and give a deep bow. The other mothers do the same. After more bowing, the established mothers either welcome the new mother to stay, or she moves on to the next knot of women. Hui remembers one woman turning up every day from 10 a.m. to 4 p.m. for a week before a group accepted her. Life inside the clique can be just as fraught.

Women feel intense pressure to secure their children's places in prestigious kindergartens, many of which require children as young as 2 to take entrance exams. According to social commentator Angela Pagano, "Among Tokyo's middle class, a child's education reflects back on the mother. Many women feel that their only means of expressing their self-worth is through their children." And while parents have to be wealthy to pay the high fees for top schools, the right connections are just as important.

"I think these women have simply never grown up," comments Miwako Nakajima, the author of Park Debut, a novel about Japan's mommy cliques. "In many ways, they seem to be locked in their own youths-the way they still bully through ostracism and have a 'leader' of the group."

Others argue that the clique is a valuable source of companionship. "We work like a support group for each other. Of course we'd welcome other mothers if their children wanted to play with ours," says Miyuki, a 32-year-old mother from Yokohama. "We take turns driving them to school and bringing them to swimming lessons. We're friends, and I know I can rely on them."

Indeed, many women feel like part of a nurturing network. It's the aspiring members who suffer most overtly. When Mitsuko Yamada moved from the country to Tokyo's upscale district of Bunkyo, she immediately caused a stir. Her husband was a Buddhist priest rather than a high-flying businessman, and her values seemed different from those of the other residents. Stories of Yamada's kindness were legendary-how, in the park, she'd comfort other people's children when they cried and how she once made a necklace out of acorns for a disabled girl. But she also had eclectic tastes. While other mothers pushed their children around in chic strollers, Yamada rode a green bicycle that had two seats for her children. The bike was infamous among local mothers. Its style, one resident remarked, "wasn't right for the neighborhood."

Despite her quirky behavior, Yamada was accepted into a clique and became friends with the boss mom. For a few months, Yamada reveled in the relationship, but then it soured-possibly because the boss mom's daughter, Haruna, 2, passed an exam for the prestigious Otawa kindergarten, while Yamada's daughter did not. The quiet, unassuming Yamada, always dominated by Haruna's wealthy and well-dressed mother, felt as if her former friend was ostracizing her. She'd later describe how her own daughter was not allowed to play in the sandbox or take her turn at the swings, and her 5-year-old son was similarly shut out at kindergarten. Eventually, like Mie Taniguchi, Yamada snapped.

On Monday, November 22, 1999, she took Haruna from the schoolyard to a nearby public toilet, removed the little girl's scarf, and used it to strangle her. Four days later, Yamada turned herself in. In court, she expressed horror at what she'd done: "I took the life of innocent Haruna and brought sorrow to her family. I shouldn't be allowed to live."

Yamada was sentenced to 15 years in jail, but her case sparked an unexpected outpouring of sympathy. One newspaper received more than 1000 letters from mothers expressing similar feelings of loneliness and frustration."In this culture, the major interests are the husband's promotion, the children's school, and the family's overall status," says Tokyo psychiatrist Machizawa Shizuo, who adds that she has treated numerous clients who have suffered nervous breakdowns from being alienated and bullied.Murder may be an unfathomable extreme, but unless Japanese society offers greater support to young mothers, more will end up like Yamada and Taniguchi, warns Toshiko Marks, professor of multicultural understanding at Shumei University. "The stress is intolerable, and the ultimate expression of these women's rage is in the crime of killing their rivals' children. The children will bear the brunt of the pain in the future."

Taniguchi's case has yet to come to court, but she knows she faces years in prison, separated from her beloved daughter. And she is tortured by the knowledge that she has ruined other lives as well. "I want to apologize to the mothers of the two children," she told police. "I regret what I did. I pray the two children will be happy in heaven. I am sorry."

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