On Jan. 7, 42-year-old actor Mikio Osawa gave a press conference in Tokyo to announce that his 17-year-old son by his ex-wife, actress Mai Kitajima, was not his — biologically, that is.

Last summer, Osawa filed a suit in family court to sever his legal relationship to the boy after he ran a DNA test that Osawa says proves he is not his father. Both Kitajima and her son, referred to by the media as A-kun, disagree.

The tabloids love this story because Osawa used to be the leader of Hikaru Genji, Johnny’s & Associates’ roller-skating boy-band juggernaut of the late ’80s, which broke up in 1994 when Osawa quit to pursue a solo career that was never half as successful. In 1996 he married Kitajima, the daughter of Yoko Naito, one of the most popular movie stars of the ’60s, after she became pregnant with A-kun. According to showbiz pundits, the marriage effectively ended his career as an idol, if it wasn’t finished already. The couple divorced in 2005 and both have since married other people.

Osawa told reporters he carried out the DNA test because he was “worried about my genetic material” after his new wife had a stillborn child, meaning he didn’t initially suspect A-kun wasn’t his son. The showbiz press, however, thinks Osawa wants to drag his ex-wife’s name through the dirt by implying that she was sleeping with someone else just before they were married, and, in fact, Kitajima has been the victim of a lot of snarky criticism on the Internet.

On the other hand, Shukan Bunshun says that after the divorce, Osawa took custody of A-kun and subjected him to abuse until he ran back to his mother. In any case, Kitajima told the women’s magazine Josei Jishin that she will not cooperate with the family court procedure.

The fact that Osawa called a press conference to discuss what most people would deem a personal matter indicates motives that probably have more to do with maintaining his celebrity than anything else, but he has also inadvertently sparked media interest in DNA testing.

A long feature in Aera explained how the procedure can now cost as little as ¥30,000, which means it’s affordable to anyone. Until three years ago, testing was almost always requested by women who wanted to confirm the paternity of their children. In some cases, they wanted to make sexual partners take responsibility for their offspring, or to prove that an ex-husband was not the father of a child they conceived with another man even if they were married at the time of the child’s conception or birth. The family registration system (koseki) deems that the legal father of a child of a married woman is that woman’s husband at the time of birth, regardless of what she says.

But Aera points out that more and more men are carrying out DNA testing on their children, usually because they suspect their wives of cheating. One testing company told Aera that three years ago, 10 percent of its customers were men. Now it’s about 30 percent, and almost all have the tests done without their wives’ knowledge.

In many cases, customers request the test during divorce proceedings because the husband suspects his wife of being with another man and doesn’t want to pay child support. If a test confirms that there is no blood relationship between the father and the child, the parental bond is dissolved administratively on the koseki and the child loses his or her right of inheritance. An article in Shukan Post claims that, according to various testing services, 1 out of 4 tests comes back “black,” meaning the child is not the biological progeny of the customer.

However, there has also been an increase in cases where men order the test because they want custody of a child after a divorce, though according to one counselor interviewed by Aera, there’s no legal advantage to testing if the relationship is already established in the koseki. There are even some men who are happily married but think that confirming the genetic link will bring them closer to their children, and she cautions that testing “opens a Pandora’s box,” and rather than strengthening family ties, the process may actually undo them. Even paternal grandparents are apparently getting in on the act: Appalled by the way their grandchildren behave, they want to check whether these kids are really their descendants.

All this scientific inquiry may be making the government nervous, since it undermines its authority in regulating connubial behavior. The Supreme Court is now pondering a case that has already gone through the Osaka court system involving a man who used to live away from his wife due to work obligations. The wife started seeing another man and became pregnant, but since the husband was visiting home on the weekends and having sex with her, he assumed the child was his. Later, the woman asked for a divorce and the husband learned about the other man. They carried out DNA testing and the results confirmed that the ex-husband was not the child’s father.

What makes this case unusual is that the plaintiff is the child. It is the ex-wife who wants to sunder the legal relationship between the child and her ex-husband, but according to Civil Code section 772, the legal father of a child as determined by the koseki is the only party who can sue to have such a relationship dissolved. Family courts will void that relationship if both parties agree to it, but in this particular case the ex-husband wants to retain paternity, so the woman’s lawyers are asserting that it is in the “child’s interest” to be legally related to the biological father.

This law was written in the 19th century as a means of establishing “legitimacy,” which can only be conferred through the koseki. But if a scientifically administered test can prove beyond a doubt who the father is, then the government loses a good deal of authority in the matter. So while men like Mikio Osawa see the technology as a means of calling out unfaithful mates, women may see it as a way of finally kicking the government out of their bedrooms.

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