Japan's recent joint custody reform, aimed at allowing both parents to maintain a relationship after divorce, is dividing parents. Many, like Yasuyuki Watanabe who hasn't seen his daughter in 15 years, feel the previous system excluded them.

Yasuyuki Watanabe has not seen his daughter in more than 15 years. But he is not celebrating the landmark custody reform that Japan has just implemented. Until last month, Japanese law required one parent to hold sole custody of children after a divorce, leaving the other party reliant on informal goodwill or court-encouraged visitation to maintain a relationship with their child. For Watanabe, 54, the result was a system seemingly designed to exclude him, where one parent could disappear from a...