TOKYO : The dollar was on the defensive on Friday following its biggest drop in a month against major peers, as it tracked a retreat in U.S. yields from nearly three-month highs after depressed Treasury prices drew buyers. Asian stocks were mixed, with some markets tracking Wall Street gains from overnight, while Japan's Nikkei struggled after the yen rebounded strongly from a three-week trough to the dollar. Hong Kong's Hang Seng rose while mainland blue chips were flat. For the week though,