The Tokyo Family Court has ruled in favor of actor and former pop idol Mikio Osawa, who had denied any biological connection with the son he allegedly fathered with actress and ex-wife Mai Kitajima.

The case went to court last month after Osawa, former leader of the all-boy idol group Hikaru Genji, conducted a DNA test in 2013 to prove he is not the son's biological father — a claim Kitajima, 43, objected to.

The decision, handed down Thursday, ended the former couple's dispute, noting that "under the law, there is no biological relationship" between Osawa, 46, and the son, who is now 18. The son's name is being withheld as he is a minor.

A Supreme Court ruling on a separate case last year, however, stated that paternity cannot be revoked by a DNA test alone, even if the results prove no biological relationship between father and child.

Thursday's ruling, however, was also based on Civil Code section 772, which states a child must be born more than 200 days after the parents marry to be considered their legitimate child.

Kitajima's child was born in January 1997, exactly 200 days after their June 1996 marriage.

Both Osawa and Kitajima refused to comment following the court's decision.

Osawa did not reply when contacted by The Japan Times on Friday.

Osawa's move came under fire from the showbiz press, which suggested he was aiming to imply Kitajima had had other sexual partners before their marriage.

The two wed after Kitajima became pregnant with the child. After their 2005 divorce, both remarried and Kitajima ceded custody of the child to Osawa.

After Osawa's new wife gave birth to a stillborn child, Osawa explained that his decision to carry out the DNA test was out of concern over genetic defects he might possess.

However, Kitajima, who won back custody of the teen in September 2013, reportedly told celebrity gossip magazine Josei Jishin that she would not cooperate with the family court procedure.

Osawa sought mediation in a family court in 2013 to sever his legal relationship with the child, claiming that he recalled a drunk Kitajima confessing that another man was the father. But the case was brought to court last month after the two sides failed to reach a settlement.

"I raised him believing he was my son," Osawa told reporters in January last year. But he said his doubts only deepened as his son got older.