Masaki Kubota's delight at reuniting with his two sons gave way to heartbreak when the younger stared at him as if to say: "Who are you?" It was their first encounter since his wife left with the boys a year earlier -- the kind of painful separation that Japan's new parental custody rules aim to prevent. The country enacted laws last month allowing joint custody after divorce, replacing a decades-old system where it was granted to only one side, and almost always to the mother. But the change has proved polarising in a country where campaigners say women's financial vulnerabilities make sole custody a bulwark against domestic abuse. IMAGES AND SOUNDBITES ARRANGED IN SEQUENCES