The yen plunged in Asian currency markets on Monday after Japan\'s conservative opposition swept to victory in national polls, with promises from its leader to press for more central bank easing. In early Tokyo trade, the dollar bought 84.30 yen, up from 83.52 yen in New York on Friday, while the euro also climbed higher on the Japanese currency at 111.10 yen from 109.94 yen in US trade.