On Christmas Eve two years ago, Masahiro Yoshida returned to his home to find it empty. His wife had fled with their 2-year-old daughter and was seeking a divorce.

Since then, he's rarely seen his child because law grants custody to only one parent — routinely the mother. His wife has refused to allow him regular visits, accusing him of emotional swings and past verbal and sometimes physical abuse.

Yoshida, a 58-year-old musician, is among a small but growing number of divorced or separated fathers who have turned to the courts to get custody, or at least gain a right to see their children. More broadly, many are demanding a change in the law to allow joint custody, as is the case in most developed countries.